Just started first build and have some dumb questions

I am more or less following the "generic benroy plans." THe hatch design calls for a 3/8 notch to be cut in the side walls for the hatch. Do I understand correctly that this is simply a template for teh 1.5 inches spars to be cut? Will the peice I nitch out be used for anything later? Also is the notch that will then exist in the side walls to make room for trim/ weatherstripping or does it have some other purpose?
Also any good tips on bending the 1/8 luan?
Thanks for your help. The postive posts all over this forum are inspiring!
Also any good tips on bending the 1/8 luan?
Thanks for your help. The postive posts all over this forum are inspiring!