find a straight line on the wall...tile, corner, etc that should be a straight line...thats what i did with my latest mount job and it worked...

i used the tile on my shower walls...i watched the guy put the tile in and he was pretty meticulous about it..so i trusted that the grout lines were going to be straight...and it gave me vertical and horizontal lines to line up the scope...


if i eyeball it without a straight line, mine are always crooked..must be the way i hold my head on the gun as they look straight to me...and i dont notice till someone else tells me...then i'll notice they are ever so slightly crooked slightly clock wise...