MTS

For the exact measurement, you would need to cut the starting squares at 4-3/8".

But the method I prefer, fwiw, is to cut them larger, make the HST locks, and trim those down to 4" UNFINISHED.


(you always have to add at least 7/8" to the FINISHED HST block measurement to get the starting square size

while we're here, the measurement for the starting squares for QST blocks is 1-1/4" (at least) added to the FINISHED block size.

Again, I prefer to cut larger and trim down.)