Drop In T-Nuts (20 series) M3-M5

 
You've spent hours painstakingly assembling your machine from V-Slot extrusion, carefully installing every single nut and bolt. Just when you think the end is in sight, you realise you need an extra tee-nut halfway along a length of extrusion - but with other parts already bolted to it, you can't just slide one along the slot. Normally, this is the part where you start begrudgingly taking things apart again - but not if you have one of these drop tee nuts on hand!
 
Unlike other tee nuts which need to be inserted at the ends of the extrusion, these nuts can be dropped in anywhere along the length of the extrusion. When you start tightening a bolt into them they turn and grip into the extrusion.
 
There are 3 sizes on hand 3mm, 4mm and 5mm thread