How do you put a lock on a Keystone Trapdoor/Door/Chest?
First, make two keystones
To program them:
1. Make two matching sets of colored runes.
2. Shift-right-click with the keystone in your hand
3. Put runes in the slots, give it a name, click "Remember"
4. Repeat for the second keystone, making sure to get the same colored runes in the same slots
To use:
1. Right click on the Chest/Gateway/Door
2. Put one of the keystones in the top slot.
3. To activate, right click with the matching keystone in your hand.
Note: for Gateway pairs, you need three keystones instead of two -- one for each gateway and one to hold in your hand as a "key".
{Edit to add}
This was for 1.1.2/1.1.2b. I just installed 1.2.0.022 and things aren't working the same.
Sorry for any confusion.
{/Edit}