A spirit level is the most common type of leveling device. Sometimes called a bubble level, the spirit level’s name is derived from its mineral spirit-filled vials. The air bubble within the horizontal vial rests precisely in the center of the vial when the level’s edge is directly parallel with the earth’s surface. Follow these steps to determine if a surface is level.

Step 1: Keep the level dry and clean at all times. Check the edges of the level for nicks, dents, rust or dirt that would cause a false reading.

Step 2: Confirm the level is working properly by setting it on a flat surface. The bubble in the horizontal vial should be perfectly centered between the two vertical lines printed on the vial. Turn the level around so the back is now facing forward. The bubble should still be in the center of the vial. Flip the level from end to end, so the top of the level is now on the bottom. The bubble should still rest in the center of the vial. If the level fails any of these tests, it can no longer be used.

Step 3: To determine whether a horizontal surface is level, set the level atop the surface with the horizontal vial parallel to the center of the surface. Look directly at the level, with your eyes at the same height as the vial. If the spirit bubble is to the right of the vial lines, the surface slopes downward, right-to-left. If the bubble is to the left of the vial lines, the surface slopes downward, left-to-right. Make the necessary adjustments until the spirit bubble is perfectly centered between the vial lines.

Step 4: To determine whether a vertical surface is plumb, stand the level on end and press its length against the vertical surface so that the vertical vial is now horizontal at the top of the level. Look directly at the now horizontal vial. If the bubble is perfectly centered between the vial lines, the vertical surface is plumb.

Step 5: To determine whether a surface is angled at a 45 degree incline, hold the level on the surface with the center horizontal vial parallel with the center of the surface. The angled vial should now be horizontal. If the bubble is perfectly centered between the vial lines, the surface is angled at a 45 degree incline.

— Questions? Linda Cottin can be reached at hardware@sunflower.com.