Aeons 1U Heavy Duty Server Rack Rails Adjustable Mounting Depth 20-33.5 inch Universal 4-Post Rack Mount Supporting Server Shelf Rails Kit L-Shape

Whoever designed these never actually tried installing them in a real datacenter. Once you have the length adjusted, you need space to get your hands on both sides of the shelf to tighten it down, with a screwdriver on the inside and a socket on the outside, because the nuts are not captive or welded.Do yourself a favor before you install and tighten these screws down and then JB weld the nuts in place so you can tighten the screws from just the inside of the rack.

Currently using it to brace a 20-bay NAS and they are solid. 10/10 I do recommend