When you've got a bent or bowed 2x4 stud in your wall, it's difficult to lay down your drywall because of the gap created between the drywall and stud. So if you are absolutely "bent" on fixing that gap (yes, a good idea), and there are several easy methods:
Fix #1: Curve Drywall to Shape
One solution, if the gap isn't significant, is to simply bend the drywall "to shape." The drywall then takes on the curvature of the stud.
Fix #2: Block or Shim Up Curve
A cleaner, and still very simple solution, is to build up the concave portion of the stud with small blocks of wood. If you have shims handy, you can lay one shim atop the other -- in opposite directions, essentially negating the angles on the shims -- so that you have a flat block. Tap the shims onto the stud with finish nails.
Fix #3: Straighten the Stud
Finally, you can actually straighten out the entire stud. Do this by:
- With a handsaw, cut about 2 inches into the stud at about the midpoint of the bow.
- Pull the bow, straightening it. Slip a single shim into the triangular portion left by your cut.
- Cut off any excess shim.
- "Sister" the stud with a two-foot long brace of 2x4 along the side of the stud.
This third fix is applicable only to non-load-bearing walls because it involves cutting into the stud.