Guides rather than buttons... no need for locktight. There's no torque on the screws.
Here is what I use. Direct from 80/20; then modified. (# 6797 for 1010 rail, and # 6897 for 1515 rail) Low cost raw part. Takes me 10 minutes with hacksaw, sander, and drill press to finish into 1 screw or 2 screw versions. Made from UHMW-PE (plastic, very similar to Teflon, with an even LOWER sliding friction). So VERY smooth sliding in the rail, even if a little dirty. (No chance of damage to rails, like Aluminum guides.)
Only issue is you can NOT bond to the UHMW-PE. (Glue or Epoxy) SO SCREWS ARE REQUIRED. I drill out the pilot hole and then countersink for 8-32 flat-head screw.
You'll NEVER wear these out. [Well, never say never, but I have used these on machines that run 24/7 for years.]
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