I take 1/2" off the size of the unit for the finished size. If I trim HSTs or flying geese I use the Block Loc ruler.
I guess I should say I take 1/4" from all four sides. 1/2" from side to side and 1/2" from top to bottom. Which would make the finished unit 1/2" smaller all the way around, not 1" smaller in size. A 2"square would finish at 1 1/2" not 1" even though there has been 1/4" taken off four times.
