You can tell the floor is not level here, even with the angle of the shot.
More pics of contour finder tool to be added later. For now, here's a small example;
NM Grower wrote:
You can make an A-frame level without the bubble level. The two sides of the A can be any length. Mark two spots that the A-frame rests on. Mark on the cross piece where the plum bob falls. Reverse the A-frame so the legs are on the opposite spot. Mark again on the cross piece where the plumb bob falls. Halfway between the two marks is level.
That's usin' your noggin! Nice tip. I may check mine like that to be sure it's correct.
NM grower has the right method for finding level on the go.