Here is a rendering of the first 2 holders I have made: the top one is to hold my pencil and tape measure, the lower one is for the quick change bits for my drill/driver. They all have 1/4" shafts, so a 5/16" hole holds them all ...
Here is another holder the guy who wrote the article has ... this one for allen wrenches (he uses plywood for everything):
Here is another holder the guy who wrote the article has ... this one for allen wrenches (he uses plywood for everything):