Gun Port Drill Jig directions (Cont'd):

"A slot 10 MM ( .394") wide by .125" deep was milled into the block, into one of the 1.000" sides. This was to accommodate the port lid, which is 10 mm (.394). This is a close fit to insure accuracy when drilling the ear holes.

The slot also provides a location, and keying effect for the nylon toe clamp which secures the port lid during drilling

A hole was drilled and tapped for a Cap Screw. The hole is central to the 10 MM slot and 5/16" (.3125") from one end of the block. It is threaded 8-32 to accept the clamp screw, which is a Socket head Allen Cap screw by 3/4" long. The hole is 5/8" deep from the bottom of the 10 MM by .125 slot."