A basic collection of rulers,
squares, and levels should serve on most home improvement projects. But
it always helps to follow the adage “Measure twice and cut once,”
particularly when it can save an extra trip to the lumber yard for more
For measuring, you can use a classic folding carpenter’s ruler or a
measuring tape. Both are available in several lengths. The fold-out
variety takes a little time to open and close, but some models have a
handy pullout extension that makes it easy to take accurate inside
dimensions--for example, between two wall studs.
For squaring up measurements for cutting, use a combination square on
smaller boards. On larger boards and over larger areas--for example, to
check the corner of a room--use a 2-foot-long framing square.
But there are a few carpentry tricks that work as well as any tool. One
is to check for square by measuring the diagonals of a piece of plywood
or a room. If the room is square, the diagonals should be equal.
Another trick is to use the proportions of a 3-4-5 triangle. If one leg
is 3 feet long, another is 4 feet long, and the hypotenuse is 5 feet
long, the angle between the two legs will be 90 degrees. Triangulation
is practical in construction and remodeling work because it works at any
scale. You can measure the sides of the layout triangle in inches, feet,
or yards and in multiples of 3-4-5 (6-8-10, 9-12-15, and so on).
Along measuring tape is handy for layout work on walls. Most have 16-in,
centers marked in red.
The extension bar on a folding ruler makes it easy to take accurate
measurements between studs.