air bubble is to the right then the horizontal slope is to the left.
to check for the 45-degree angle the method is the same as the other two ways.
you are going to be using the spirit bubble on the 45-degree angle.
put the level parallel with the item you want to check, make sure that the level is in contact with the item all the way down the surface. check that the air bubble is between the two marked lines, which are marked at either side of the glass tube. if the bubble is closer to the top of the tube then this is at a greater angle than 45-degrees, if 