Drywall shims are thin, sturdy pieces of cardboard typically measuring 45 inches and 1/16 inch thick that can help level areas of the wall or ceiling that are uneven.

Test which areas require a drywall shim with a laser-level or straight-edge tool. If you see a gap, this area needs to have a shim or more, depending

on the size.

Since it doesn’t connect to the drywall, shims need to be stapled, nailed, or screwed into a stud. Use multiple pieces if the gap is large, but securing them may be harder.

Adding thickness will also weaken the connection between the drywall and stud, so try to limit the number of shims in any area to create a consistent surface for even installation.

While you can use drywall shims in different areas, avoid places that experience high moisture levels, as the cardboard material is absorbent and prone to mold or mildew buildup.

If you need shims in high moisture areas, other types made from different materials, such as stainless steel, are available, but they have a higher cost.