This shim can be adjusted up to around 125% its original height using a screwdriver. Each shim requires two of the pieces printed the same size, plus a #6-32 machine screw and hex nut set of an appropriate length. See instructions for details.
This can be used for furniture making (I developed it to fine-tune drawer slide rails), for leveling, etc.
Version 3 adds the option of screw holes so one or both sides can be attached - may be useful for woodworking applications.
Print two of the shim pieces and put them together with the shiny sides facing each other (the side that was facing down during the print).
Insert a #6-32 machine screw through the slot and secure with a hex nut on the other end. Try to match the size of the machine screw to the length, e.g. use 1.5 inches for the default 39mm (1.5 inch) length.
Apologies for the unit hodgepodge but all units are currently mm (millimeters). 26mm is about 1 inch, 39mm 1.5 inches, 52mm 2 inches, etc.
Use your regular infill setting or slightly denser. The default honeycomb fill pattern slic3r generates is actually quite strong although the print orientation slants it a bit.
Note that when adjusting the shim the slot should allow the height to expand up to about 125% the original height. Going beyond that will have some of the machine screw sticking out and pointing down.