Your gonna Laugh, but my sanding block is 1/8" thick
aluminum , (1" X 2"). i have 3 of them:
1) the exact length of my sandpaper
2) the exact Width of the papar, (i get 3 pieces of
sandpaper,after folding the edges)
3) is 1/2 the length of # 2.

Every time you drop your sanding block on the floor
then sand all 4 sides with 100grit by using one of
the other blocks. Do NOT forget this or your sanding job
will be screwed !!

Bille