1515 Tee Nuts

thingiverse

These tiny stoppers keep M3 nuts from slipping into 1515 extrusion channels and position them closer to the channel's face, making them easier for M3 screws to grasp. The hole in the back is slightly undersized, giving it a nyloc-like effect. They should also work with M3 hex nuts. I printed them using PLA material. Note that they're designed for 0.2mm layer height and require a 0.3mm first layer. If you use 0.2mm for your first layer, scale the design up by 0.1mm in Z direction before printing with your slicer. The F360 source is included if you need to make any adjustments.