I have a mic and a digital dial indicator and had to make a holder out of wood to hold the indicator but to measure the entire surface of an 8x10 film holder the wood holder would have to be really long.

Does anyone have a good setup for measuring the depth of film holders? Given the build of a film holder, putting it on a level table, like my shaper or table saw and using a magnetic base would not work as it would place the surface of the opposite side of the holder on the table and not measure the septum to seating edge of the holder.