Patch—thickness of channel Channel Trimmed area Drill No. 30 (0.128") Rivets Finished Repair Patch angle—thickness of channel Channel Trimmed area Patch angle—thickness of channel Drill No. 30 (0.128") 1/2" spacing (approximate) Finished Repair Rivets Figure 4-197.  Channel repair by patching. Figure 4-198.  Channel repair by insertion. 4-114