How to Use a Combination Square

What You'll Need
Combination square with square head
Wooden board (size will depend on the project)

Widely regarded as a functional and indispensable tool for the workshop, the combination square should be present in the toolbox of most DIY enthusiasts who have a love for carpentry. The combination square is a versatile tool that is used not only in carpentry, but in metal works and stone masonry as well. The combination square is a simple device with a lot of uses and could come with different heads. High-end models have an angle finder, a center head and a protractor head. But, the basic combination square comes with what is known as the square head or angle head. The angle head could be used to measure angles of 45 and 90 degrees, to check for square and also act as a leveling device as the angle head comes with a leveling vial. The tool consists of a ruled blade similar to a ruler that is used for various measurements. It has markings for both inches and millimeters to conform to any unit of measure. The heads are interchangeable and are used to measure angles, find the center of circles and as an accurate marking device. The following instructions will show how to use a combination square for cross cutting, marking a parallel line and to check for square.

Step 1 - How to Mark a Board for Cross cutting

Crosscutting is the process of cutting a board perpendicular or across the grain and could simply be referred to cutting a board to length. If the width of the board is 12 inches or less then using a combination square to mark the board will result to a clean and straight cut. Simply place the combination square on the board and draw a line across the blade using a sharp pencil as you would use a ruler. If the board is more than 12 inches in length, follow these simple steps:

  1. Place the square head on the edge of the board.
  2. Loosen the adjustment nut to move the blade to the desired measurement. Re tighten the nut after measuring.
  3. Use a pencil and place the tip on the edge of the blade. Most combination squares have a slight notch on the center of the blade end to properly hold the tip of the pencil in place.
  4. Using the square as a guide, slide the combination square along with the pencil to properly mark a straight line. Hold the square against the material and the pencil against the end of the blade.
  5. Follow the line that you've drawn when cutting the wood.

Step 2 - How to Mark a Line Parallel to the Edge of the Board

The same procedure as for cross cutting a board can be utilized when marking a parallel line. Remember to place the square parallel to the material to serve as a guide.

    • Configure the combination square to the desired measurement.
    • Place a pencil on the special marking at the tip of the blade.
    • Slide the combination square along with the pencil to mark a parallel line. 

      Step 3 - How to Check For Square

      Since the square head is used to measure angles of 45 and 90 degrees and a proper square has 90 degree angles on each side, follow these steps to check for square.

      1. Place the combination square on the edge of the material to check the proper square.
      2. Set the flat edge of the square head on a horizontal surface to determine increments in a square. This procedure could also be used to check for the level in your material.