Keuffel & Esser co. Slide Rules produced prior to 1945 suffer from a plastic-like material (bakelite?) that rots over time. The glass cursors mount on two small rectangular blocks (one on each side of the rule). The goal of this entry is to provide suitable replacements so one can repair their rule and make it useful again. (Why do this? These instruments helped engineers put us on the moon!)
Parts were designed in FreeCAD. Source file included.
Printed two with the slot feature facing upward. The slots are intended for a spring to keep things tight and aglined, but I have almost a perfect fit with my rule. If it is loose on yours then use a spongy material or a piece of zip tie to make a spring in the slots to keep things nice and tight.
Printed on a Printrbot Simple 1401 maker's edition with 0.4mm nozzle, 0.2 mm layer height, @ 195 deg C on slow speed settings.
The image of a damaged cursor assembly was taken from: http://www5b.biglobe.ne.jp/~tomozawa/en/sr-annex/ke-cursor/kercse.htm. (Mine was basically dust after I took it apart.)