This was a fix for a friend. I'm sure you've seen those large umbrellas that slip through the hole in a center of a patio table. Some of them have an elbow joint near the top that allows the umbrella to tilt at an angle. There's a locking mechanism that is supposed to allow the user to lock the umbrella in the straight position, but sometimes it wears out or is just plain defective.

This little clip on sleeve makes it possible to easily lock the joint by clasping it around the joint, effectively preventing the elbow from flexing whether it's locked or unlocked. You can slide it up or down to restore the elbow's functionality. Also it's easy to remove if necessary.

This sleeve fits shafts with a diameter of 34mm. I did print one out and test it, and it worked perfectly, just forgot to take a picture. I recommend printing with increased wall loops and a small foot support, otherwise it might detach from the build plate before it's done printing. I tried uploading the gcode, but for some reason Printables keeps rejecting my P1P gcode.