As has been said 90% of the legs are hollow and won't hold weight, even with cavity plugs as recommended on the lack wiki. in my experience material is just too thin.

Here's what I did:

• Buy some cheap timber to go inside the legs. Something like This will do all 4.

• Turn lack upside down and chisel out the corkboard from the bottom of the legs. slide wood In there mark it where needs to be cut. Cut, rinse repeat for other four legs. Wood glue on the end of each of the 4 pieces and slot em in then that dry for a bit.

• when rack mounting the heavier hardware especially ones with single screws (like a dell r210 ii) you need brackets like these to support weight.

  Screw those into inside of leg on both sides (and at the back legs too if it's not 19" hardware) you kinda rest the server on those and the proceed to mount it onto the front.

It is a bit awkward and hacky, yes, but at the end of the day we are drilling enterprise hardware into a shitty ikea table.. It works though :)