First, give Garrett the lockpicks (Doh !). Use LockPickSM and LockPickLG rather than BothLockPicks.
Then, make the door, chest or whatever you want to be picked. Select it and press the "properties" button.
Add "engine features : Locked" and check the box, then add "Dark gamesys : PickCfg"

Now edit PickCfg. There are 3 different possible stages of the lock, and each has 4 settings. If you leave all of these settings on a stage blank, that stage will be ignored.

LockBits : This specifies which pick will work with this stage. 0 means neither will work, 1 means the Square-toothed will work, 10 means the Triangle-toothed one will work, and 11 means either will work.

Pins : This is the number of pins in this stage of the lock. Eack pin inside a stage is picked with the same pick, and makes a click once it is picked.

TimePct : I think this is the time it takes to pick each pin in the stage.

Flags : I can’t tell what "reset on fail" does. "Randomise time" appears to, as you would expect, randomise the time taken to pick each pin.

An Example :

For a lock on which you have to change picks once, and the second stage takes longer than the first :

LockBits 1-----1
Pins 1---------2
TimePct 1------1
Flags 1--------[none]

LockBits 2-----10
Pins 2---------5
TimePct 2------1
Flags 2--------[none]

Lockbits 3-----0
Pins 3---------0
TimePct 3------0
Flags 3--------[none]