Question: I have a concrete floor and I made two holes to bolt a 1/4"-thick steel plate. The problem is that the steel plates haven't been drilled yet.

How can I determine where the holes will be drilled in the steel plates so they match the holes in the concrete?
[![enter image description here](https://i.stack.imgur.com/1Kt5n.png)](https://i.stack.imgur.com/1Kt5n.png)

Answer: 
The usual methods are:

1. Careful measurement. Really this doesn't need to be that precise, you are not looking for a press-fit between bolts and clearance holes.

If it goes wrong, just elongate a hole into a slot using whatever tools you have to hand (e.g. a round file, clapped-out old Bridgeport, ...) - Remember: "A grinder *file/filler* and paint make me the welder machinist I ain't".
2. Put pointy or painty things into the holes then press the steel plate down in place to mark it. In the dead-tree-carcass world there are things called "dowel pins" used for this kind of thing.
Since nobody else has mentioned it, I'll add another option that I've used in the past for spacing holes.

1. Put some paint on the floor around the holes.
2. While the paint is still wet, place the metal plate on the floor.

When you remove the metal plate from the floor, the wet paint will have transferred to the plate but will leave two spots behind where the holes were. Mark those spots, clean up the wet paint, and drill.

This also works great for spacing screw holes for handles on cabinets & drawers although I would usually use lipstick for those instead of paint.