Thread: Securing a pistol safe

Heavy channel is C-shaped in section so it can be narrow enough that it is harder to nose an angle grinder in there from below - this is assuming that the c-shape is pointing down so that it looks like an "n" if that makes sense

If you don't have room to get in underneath then this advice is all moot

If there is no access from under then a hole in the floor and boxing up a square underneath would work - get some threaded rod say 16mm galv, bend it so that it resists pullout and embed it in the concrete

The way I'd do it is to cut a ply template of the holes in the bottom of the safe and use that ply to hold the -presumably 4- rods in place while the concrete sets. You'd need a hole in the middle to pour the concrete through.
Bend your steel cage up to your satisfaction then tie in your rods, drop 4 nuts in to set height then slide the ply down and secure with 4 nuts on top of the ply
plastic tape over the rods will keep concrete off the threads
pour concrete, add lots of cement, don't buy that rapidset premix stuff it is shite
Rod the concrete or vibrate it to get rid of all the air pockets then leave it for a week
take off tape, lift off ply, use some expanding foam around the gaps to stop vermin
Don't forget dampcourse/malthoid/DPC on top of the concrete to stop moisture coming up and corroding the steel - the "tarpaper" style is better than that plastic crap

I'd recommend a thick layer of grease between the malthoid and the base of the safe to prevent rust and bolt that baby down tight

If rods are too long you can cut them off from inside the safe after it is bolted down