How do you use a Tubular Decoder Key?

very simple. it measures the depth of the slot. the ACE style tubular key has 7 pin slots. So looking at the end of the key you put in the lock, counting clockwise,

position 1 through 7. so position 1 might have a depth of "3",

position 2 might be 7, and so on. depth is measured how long the cut is made tward the handle of the key. it is used to replicate an existing key.

Hope this helps .

Dan.