Carpentry 101: Scribe for a Better Fit
Ever try to fit a counter top or even a piece of shelving flush against a wall? Chances are it didn't end up exactly right, probably because the wall wasn't straight or it was uneven. Either way, you were left with the choice of leaving that gap (and hoping no one would notice) or applying a bead of caulk to cover it. Experienced carpenters (who can fit things against walls) know the way to fit flush with a wall requires a simple technique called scribing. It's straightforward, easy to learn, and best of all, the tools don't cost much. Here's the basics on how you go about scribing to achieve a nice tight fit, and after a little practice, your work will look like it was done by a pro.
Scribing on a Counter Top
Start by aligning your work piece properly (i.e., be sure it's level), and position it as closely as possible to its final location. Place your compass so the point is against the wall while the pencil is aligned with the widest portion of the gap between the wall and the edge of your work piece, then tighten the set screw—locking the compass in position. Keeping the compass point against the wall, draw a line the width of your counter top. The pencil line you draw will match exactly to the outline of the wall. Now, all you have to do is move the piece away from the wall and use your belt sander with 80 or 100-grit sandpaper (or a jig saw) to remove the excess material right to the pencil line. Be sure you work slowly and take the time to test fit the piece as you remove the excess to ensure the final edge aligns perfectly with the wall.
It helps to undercut the edge of the counter top when you get close to the line—this will make final positioning of the piece easier.
Scribing for Wainscoting
When installing wainscoting or anything vertically against a wall, you'll often find out that your walls aren't perfectly plumb. In these cases, you just need to apply the scribing technique in a slightly different way.
Position your wainscoting close to the wall (but not touching) and use a level to ensure the wood piece is plumb. Position the point of your compass against the wall again and run the line the length of the wainscot. Now, just cut away or sand off the excess. The cut side will fit flush against the wall, while the uncut edge will be perfectly vertical. You can now install the rest of your wainscoting flush against the first piece, knowing it will be plumb.
Scribing to Fit Between Two Walls
Cut your work piece to about 1/2 inch longer than the distance between the walls. Then, position it against the back wall and against one end (on an angle). Run your scribe line and remove the excess. Reposition your work piece and do the same thing at the other end.
A Few Quick Tips
If the gap between your piece and the wall is small, you might not even need a compass. Just position the pencil itself against the wall and draw your line on the work piece.
Lost your compass? Tape a piece of wood onto your pencil and place it against the wall and then draw your line. The mark will follow the profile of the wall exactly.
Finally, be sure you keep the pencil perpendicular to the work you are marking. If you change the angle while drawing the line, the profile line won't be consistent over its entire length.