HAMMER T NUT, M4 THREAD, 8MM SLOT, ZINC PLATED, CARBON STEEL (PACK OF 100) | Torus Group
Steel Pinch Clamp with 7mm Slot and M6 Thread
L-A M8 x 30mm Thread T Slot Drop-in Bolt T-Bolt Hammer Head Bolt T Screw Stud for 4040 Series Standard 8mm T-Slot Aluminum Extrusion Profile (4040 Series, 20 Pcs) : Amazon.co.uk: DIY
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mechanism - How does the Makeblock threaded slot work? - Robotics Stack Exchange