I needed a "height gage" to set the protrusion of bits on my
(woodworking) router and for some other applications.  I got somewhat
carried away and made the pieces pictured.  The crenelated tower
on the right has slots of varying length cut into it.  When the middle
piece is dropped into this tower, the rectangular arm can drop into any
of these slots which places the bottom of the arm a fixed height above
the surface in increments of 1/8" from 2" to 1-1/8".  The cylindrical
rod attached to the arm is 1" long so the measurement range is extended
to 1/8" to 2".  A 1/16" shoulder at the end of the arm allows one to get
measurements in increments of 1/16".  The threaded rod is for "oddball
measurements" that one wants to remember and duplicate.