Minecraft wiki entry for Combination_locks, associated text: Item frame combination locks are a step up in complexity from lever locks. Items in item frames can be rotated into 8 different positions. This rotation can be detected by a comparator which will output a signal strength from 1 to 8 depending on the position. Since each item frame has 8 possible states, the number of possible combinations can be found with 8n, where n is the number of item frames.