My quick-fix is to just hide the sketch - will this cause me issues later on?

I learned 3d modeling with different software, and to do this, all I had to do was use smart-dimension and change the distance between the two points (the center of the hole, and the edge of the plate) - but on here, the distance part of smart dimension is grayed out, and I haven't figured out how to make it work.

I have a one-inch thick plate, and I'm trying to put screw/bolt holes 1.5" in from each corner. I know how to make the holes, but whatever I've used to get the holes to the specific spot, I need to remove afterwards - and it always gives relations no longer exist errors.

What I've tried:

-Smart-dimension-ed between the center of the hole and the side of the plate, and tried to change the distance --> grayed out dimension box

-Make a 1.5" line from each corner, then put the holes on top of the ends of the lines, then remove the original lines --> relations missing error

-Make a rectangle from the center of the plate and put holes on each corner, then delete the rectangle --> relations missing error

This isn't the first time I've had 'relations to missing geometry' errors a lot, but I can usually find a way around them - it would be nice if I could avoid them altogether.

Message was edited by: John Jagiella Added part - if I remove the lines I added from the corners, I get errors. Ignore the rectangle in the middle, I'm using that to line up another piece in an assembly. (Also, I don't know what 'construction lines' are, or at least how to use them)