Recently there was a discussion about using a plunge router along with
a home made jig to make a mortise.

Jig is simple enough; however, proper set up could be a little touchy
since there are no centerlines, scales, etc to assist.

Tonight I'm scrounging thru a desk drawer and find some 8x8 grid paper
used for graphic arts layouts.

BINGO.

Tape a piece of the 8x8 to the bottom plate with double back tape,
then overcoat with a sheet of clear contact paper used to protect
books, shelves, etc.

Now you have a reference grid to use for any set up that is protected
which reduces accurate set up to a minimum.

Even a blind hog finds an acorn if he keeps rooting around long enough.

Lew