diff --git a/keyboards/bastardkb/skeletyl/keymaps/quotengrote/features/layer_lock.c b/keyboards/bastardkb/skeletyl/keymaps/quotengrote/features/layer_lock.c
new file mode 100644
index 0000000000..1a58378e75
--- /dev/null
+++ b/keyboards/bastardkb/skeletyl/keymaps/quotengrote/features/layer_lock.c
@@ -0,0 +1,146 @@
+// Copyright 2022-2023 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+/**
+ * @file layer_lock.c
+ * @brief Layer Lock implementation
+ *
+ * For full documentation, see
+ * <https://getreuer.info/posts/keyboards/layer-lock>
+ */
+
+#include "layer_lock.h"
+
+// The current lock state. The kth bit is on if layer k is locked.
+static layer_state_t locked_layers = 0;
+
+// Layer Lock timer to disable layer lock after X seconds inactivity
+#if LAYER_LOCK_IDLE_TIMEOUT > 0
+static uint32_t layer_lock_timer = 0;
+
+void layer_lock_task(void) {
+  if (locked_layers &&
+      timer_elapsed32(layer_lock_timer) > LAYER_LOCK_IDLE_TIMEOUT) {
+    layer_lock_all_off();
+    layer_lock_timer = timer_read32();
+  }
+}
+#endif  // LAYER_LOCK_IDLE_TIMEOUT > 0
+
+// Handles an event on an `MO` or `TT` layer switch key.
+static bool handle_mo_or_tt(uint8_t layer, keyrecord_t* record) {
+  if (is_layer_locked(layer)) {
+    if (record->event.pressed) {  // On press, unlock the layer.
+      layer_lock_invert(layer);
+    }
+    return false;  // Skip default handling.
+  }
+  return true;
+}
+
+bool process_layer_lock(uint16_t keycode, keyrecord_t* record,
+                        uint16_t lock_keycode) {
+#if LAYER_LOCK_IDLE_TIMEOUT > 0
+  layer_lock_timer = timer_read32();
+#endif  // LAYER_LOCK_IDLE_TIMEOUT > 0
+
+  // The intention is that locked layers remain on. If something outside of
+  // this feature turned any locked layers off, unlock them.
+  if ((locked_layers & ~layer_state) != 0) {
+    layer_lock_set_user(locked_layers &= layer_state);
+  }
+
+  if (keycode == lock_keycode) {
+    if (record->event.pressed) {  // The layer lock key was pressed.
+      layer_lock_invert(get_highest_layer(layer_state));
+    }
+    return false;
+  }
+
+  switch (keycode) {
+    case QK_MOMENTARY ... QK_MOMENTARY_MAX:  // `MO(layer)` keys.
+      return handle_mo_or_tt(QK_MOMENTARY_GET_LAYER(keycode), record);
+
+    case QK_LAYER_TAP_TOGGLE ... QK_LAYER_TAP_TOGGLE_MAX:  // `TT(layer)`.
+      return handle_mo_or_tt(QK_LAYER_TAP_TOGGLE_GET_LAYER(keycode), record);
+
+    case QK_LAYER_MOD ... QK_LAYER_MOD_MAX: {  // `LM(layer, mod)`.
+      uint8_t layer = QK_LAYER_MOD_GET_LAYER(keycode);
+      if (is_layer_locked(layer)) {
+        if (record->event.pressed) {  // On press, unlock the layer.
+          layer_lock_invert(layer);
+        } else {  // On release, clear the mods.
+          clear_mods();
+          send_keyboard_report();
+        }
+        return false;  // Skip default handling.
+      }
+    } break;
+
+#ifndef NO_ACTION_TAPPING
+    case QK_LAYER_TAP ... QK_LAYER_TAP_MAX:  // `LT(layer, key)` keys.
+      if (record->tap.count == 0 && !record->event.pressed &&
+          is_layer_locked(QK_LAYER_TAP_GET_LAYER(keycode))) {
+        // Release event on a held layer-tap key where the layer is locked.
+        return false;  // Skip default handling so that layer stays on.
+      }
+      break;
+#endif  // NO_ACTION_TAPPING
+  }
+
+  return true;
+}
+
+bool is_layer_locked(uint8_t layer) {
+  return locked_layers & ((layer_state_t)1 << layer);
+}
+
+void layer_lock_invert(uint8_t layer) {
+  const layer_state_t mask = (layer_state_t)1 << layer;
+  if ((locked_layers & mask) == 0) {  // Layer is being locked.
+#ifndef NO_ACTION_ONESHOT
+    if (layer == get_oneshot_layer()) {
+      reset_oneshot_layer();  // Reset so that OSL doesn't turn layer off.
+    }
+#endif  // NO_ACTION_ONESHOT
+    layer_on(layer);
+#if LAYER_LOCK_IDLE_TIMEOUT > 0
+    layer_lock_timer = timer_read32();
+#endif  // LAYER_LOCK_IDLE_TIMEOUT > 0
+  } else {  // Layer is being unlocked.
+    layer_off(layer);
+  }
+  layer_lock_set_user(locked_layers ^= mask);
+}
+
+// Implement layer_lock_on/off by deferring to layer_lock_invert.
+void layer_lock_on(uint8_t layer) {
+  if (!is_layer_locked(layer)) {
+    layer_lock_invert(layer);
+  }
+}
+
+void layer_lock_off(uint8_t layer) {
+  if (is_layer_locked(layer)) {
+    layer_lock_invert(layer);
+  }
+}
+
+void layer_lock_all_off(void) {
+  layer_and(~locked_layers);
+  locked_layers = 0;
+  layer_lock_set_user(locked_layers);
+}
+
+__attribute__((weak)) void layer_lock_set_user(layer_state_t locked_layers) {}
diff --git a/keyboards/bastardkb/skeletyl/keymaps/quotengrote/features/layer_lock.h b/keyboards/bastardkb/skeletyl/keymaps/quotengrote/features/layer_lock.h
new file mode 100644
index 0000000000..a0f1455ac8
--- /dev/null
+++ b/keyboards/bastardkb/skeletyl/keymaps/quotengrote/features/layer_lock.h
@@ -0,0 +1,136 @@
+// Copyright 2022-2023 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+/**
+ * @file layer_lock.h
+ * @brief Layer Lock, a key to stay in the current layer.
+ *
+ * Overview
+ * --------
+ *
+ * Layers are often accessed by holding a button, e.g. with a momentary layer
+ * switch `MO(layer)` or layer tap `LT(layer, key)` key. But you may sometimes
+ * want to "lock" or "toggle" the layer so that it stays on without having to
+ * hold down a button. One way to do that is with a tap-toggle `TT` layer key,
+ * but here is an alternative.
+ *
+ * This library implements a "Layer Lock key". When tapped, it "locks" the
+ * highest layer to stay active, assuming the layer was activated by one of the
+ * following keys:
+ *
+ *  * `MO(layer)` momentary layer switch
+ *  * `LT(layer, key)` layer tap
+ *  * `OSL(layer)` one-shot layer
+ *  * `TT(layer)` layer tap toggle
+ *  * `LM(layer, mod)` layer-mod key (the layer is locked, but not the mods)
+ *
+ * Tapping the Layer Lock key again unlocks and turns off the layer.
+ *
+ * @note When a layer is "locked", other layer keys such as `TO(layer)` or
+ * manually calling `layer_off(layer)` will override and unlock the layer.
+ *
+ * Configuration
+ * -------------
+ *
+ * Optionally, a timeout may be defined so that Layer Lock disables
+ * automatically if not keys are pressed for `LAYER_LOCK_IDLE_TIMEOUT`
+ * milliseconds. Define `LAYER_LOCK_IDLE_TIMEOUT` in your config.h, for instance
+ *
+ *     #define LAYER_LOCK_IDLE_TIMEOUT 60000  // Turn off after 60 seconds.
+ *
+ * and call `layer_lock_task()` from your `matrix_scan_user()` in keymap.c:
+ *
+ *     void matrix_scan_user(void) {
+ *       layer_lock_task();
+ *       // Other tasks...
+ *     }
+ *
+ * For full documentation, see
+ * <https://getreuer.info/posts/keyboards/layer-lock>
+ */
+
+#pragma once
+
+#include "quantum.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * Handler function for Layer Lock.
+ *
+ * In your keymap, define a custom keycode to use for Layer Lock. Then handle
+ * Layer Lock from your `process_record_user` function by calling
+ * `process_layer_lock`, passing your custom keycode for the `lock_keycode` arg:
+ *
+ *     #include "features/layer_lock.h"
+ *
+ *     bool process_record_user(uint16_t keycode, keyrecord_t* record) {
+ *       if (!process_layer_lock(keycode, record, LLOCK)) { return false; }
+ *       // Your macros ...
+ *
+ *       return true;
+ *     }
+ */
+bool process_layer_lock(uint16_t keycode, keyrecord_t* record,
+                        uint16_t lock_keycode);
+
+/** Returns true if `layer` is currently locked. */
+bool is_layer_locked(uint8_t layer);
+
+/** Locks and turns on `layer`. */
+void layer_lock_on(uint8_t layer);
+
+/** Unlocks and turns off `layer`. */
+void layer_lock_off(uint8_t layer);
+
+/** Unlocks and turns off all locked layers. */
+void layer_lock_all_off(void);
+
+/** Toggles whether `layer` is locked. */
+void layer_lock_invert(uint8_t layer);
+
+/**
+ * Optional callback that gets called when a layer is locked or unlocked.
+ *
+ * This is useful to represent the current lock state, e.g. by setting an LED or
+ * playing a sound. In your keymap, define
+ *
+ *     void layer_lock_set_user(layer_state_t locked_layers) {
+ *       // Do something like `set_led(is_layer_locked(NAV));`
+ *     }
+ *
+ * @param locked_layers Bitfield in which the kth bit represents whether the
+ *                      kth layer is on.
+ */
+void layer_lock_set_user(layer_state_t locked_layers);
+
+/**
+ * @fn layer_lock_task(void)
+ * Matrix task function for Layer Lock.
+ *
+ * If using `LAYER_LOCK_IDLE_TIMEOUT`, call this function from your
+ * `matrix_scan_user()` function in keymap.c. (If no timeout is set, calling
+ * `layer_lock_task()` has no effect.)
+ */
+#if LAYER_LOCK_IDLE_TIMEOUT > 0
+void layer_lock_task(void);
+#else
+static inline void layer_lock_task(void) {}
+#endif  // LAYER_LOCK_IDLE_TIMEOUT > 0
+
+#ifdef __cplusplus
+}
+#endif
diff --git a/keyboards/bastardkb/skeletyl/keymaps/quotengrote/keymap.c b/keyboards/bastardkb/skeletyl/keymaps/quotengrote/keymap.c
index 1d44274dff..888ef84485 100644
--- a/keyboards/bastardkb/skeletyl/keymaps/quotengrote/keymap.c
+++ b/keyboards/bastardkb/skeletyl/keymaps/quotengrote/keymap.c
@@ -1,5 +1,6 @@
 #include QMK_KEYBOARD_H
 #include "keymap_german.h"
+#include "features/layer_lock.h"
 
 // rgb
 void keyboard_post_init_user(void) {
@@ -36,6 +37,12 @@ bool rgb_matrix_indicators_advanced_user(uint8_t led_min, uint8_t led_max) {
   return false;
 }
 
+// layer lock
+// https://getreuer.info/posts/keyboards/layer-lock/index.html
+enum custom_keycodes {
+  LLOCK = SAFE_RANGE,
+};
+
 // combos; https://github.com/qmk/qmk_firmware/blob/master/docs/feature_combo.md
 enum combos {
   C_AE,
@@ -99,7 +106,7 @@ const uint16_t PROGMEM keymaps[][MATRIX_ROWS][MATRIX_COLS] = {
   [3] = LAYOUT_split_3x5_3(
       XXXXXXX, KC_HOME, KC_UP,   KC_PGUP,  XXXXXXX,          XXXXXXX, KC_PGUP, KC_UP,   KC_HOME,  KC_BSPC,
       KC_TAB,  KC_LEFT, KC_DOWN, KC_RIGHT, XXXXXXX,          XXXXXXX, KC_LEFT, KC_DOWN, KC_RIGHT, KC_DEL,
-      XXXXXXX, KC_END,  KC_PGDN, XXXXXXX,  XXXXXXX,          XXXXXXX, KC_PGDN, XXXXXXX, KC_END,   XXXXXXX,
+      XXXXXXX, KC_END,  KC_PGDN, XXXXXXX,  LLOCK,            LLOCK, KC_PGDN, XXXXXXX, KC_END,   XXXXXXX,
                         XXXXXXX, _______, _______,            _______, _______, XXXXXXX
   ),
   // Media - yellow
@@ -157,6 +164,8 @@ bool process_record_user(uint16_t keycode, keyrecord_t *record) {
                 return false;
             }
             return true;
+    // layer lock
+    if (!process_layer_lock(keycode, record, LLOCK)) { return false; }
     }
     return true;
 }
diff --git a/keyboards/bastardkb/skeletyl/keymaps/quotengrote/rules.mk b/keyboards/bastardkb/skeletyl/keymaps/quotengrote/rules.mk
index dc68f099de..26c4522491 100644
--- a/keyboards/bastardkb/skeletyl/keymaps/quotengrote/rules.mk
+++ b/keyboards/bastardkb/skeletyl/keymaps/quotengrote/rules.mk
@@ -2,3 +2,4 @@ CAPS_WORD_ENABLE = yes
 AUTO_SHIFT_ENABLE = yes
 COMBO_ENABLE = yes
 RGB_MATRIX_ENABLE = yes
+SRC += features/layer_lock.c