How to Use a Carpenter Square

PDF download Download Article
PDF download Download Article

A carpenter square, also sometimes known as a framing square or speed square, is a type of carpentry tool commonly used by carpenters, builders, and other home improvement aficionados. A quick check with a carpenter square gives you the ability to measure and mark precise angled dimensions for complex projects like roofs, rafters, and stairways. In order to get the most accurate reading possible and ensure a job well done, it’s important to know the various ways to employ your carpenter square.

Method 1
Method 1 of 2:

Measuring with a Carpenter Square

PDF download Download Article
  1. The right-angle leg perpendicular to the base is designed to double as a standard ruler—simply use it the same way you would any other ruler. This will allow you to measure straight lines up to 7–12 inches (18–30 cm) in length, depending on the model you’re using. [1]
    • For measurements longer than 7–12 inches (18–30 cm), you’ll be better off reaching for a yardstick or tape measure.
  2. The pivot point is the corner of the square where the two 90-degree legs meet. Press the fence against the edge of the board and use one finger to hold the pivot point steady. Carefully swing the tool outward along the board until you reach the desired angle on the leg opposite the pivot point. Mark the angle on the board using a pencil. [2]
    Advertisement
  3. Determine roof pitch fast using a carpenter square and torpedo level. Align the pivot point with the outer edge of the roof where it meets the side of the structure, making sure the fence is facing up. Hold a torpedo level flat against the lip of the fence and adjust the height of the square until the bubble inside the level is centered. The point on the opposite leg of the square where it meets the roof’s surface will tell you the pitch. [4]
    • On most carpenter squares, the numbers indicating pitch can be found directly above those used to measure angles.
    • Pitch is given as a single number, which is meant to be read in a rise-over-run format. If you get a measurement of 7, for example, it means the actual pitch of your roof is 7/12, or 7 inches (18 cm) of height (rise) for every 12 inches (30 cm) of length (run). [5]
  4. Hold the tool up to the squared edge to confirm whether the cuts or members on either side are exactly perpendicular to one another. If you discover that they’re not, trace along the right-angle legs of the square and use the markings to trim, shape, or re-set the components as needed. [6]
    • If one edge of a cut is off by a small margin, it may be easier to shave it down with a power planer than to try to cut away the excess material using a saw. [7]
    • Anytime you're working with materials that form a right angle to one another, it's a good idea to check them with your carpenter square along with your level.
    5. Advertisement
Method 2
Method 2 of 2:

Marking and Guiding Cuts

PDF download Download Article
  1. Hold the fence, or the leg with the elevated lip, flush against the long edge of your board. Then, run a pencil down the perpendicular leg of the square to draw a straight line across the board. Saw along this line to ensure that the ends of your boards have been cut to an exact 90-degree angle. [8]
    • Another advantage of the raised fence is that it holds the tool in place, making it less likely to shift and throw off the angle of your markings.
    • This will likely be the feature of your carpenter square that you'll rely on most often, as the majority of the cuts used to shape building lumber are cross-cuts made at a 90-degree angle.

    Tip: Learning to quick-set the fence of your carpenter square can take the difficulty out of making repetitive square cuts for things like wall studs , floor joists , and stair stringers . [9]

  2. The diagonal leg is the one that bisects that right angle formed by the fence and the perpendicular ruler leg. Line up the pointed end of the fence with the vertical edge of your material (or another straight marking). Trace along the tool’s diagonal leg to quickly mark a perfect 45-degree angle. [10]
    • If you just used your square to mark a 90-degree cut line, you’ll need to flip it over in order to draw an angled line from the same starting point. [11]
    • Being able to mark 45-degree cut lines quickly makes it much easier to fashion corner joints for things like door and window frames, cabinets, and furniture components.
  3. The 1 ⁄ 4  in (0.64 cm) notches located on the interior of the triangle are used for marking lengthwise cuts on lumber. Set the fence against the edge of the board to frame it at 90 degrees and select the slot you want to use. Insert the tip of your pencil into the slot and slide the square down the board slowly to draw a line parallel to the board’s edge. This indicates where you need to cut along its length. [12]
    • Be sure to use the slot that most closely corresponds to the measurements of your planned cut, keeping in mind that the slots are precise up to 1 ⁄ 4  in (0.64 cm).
    • The line scriber feature can be useful when you need to rip boards to a thinner width or make notched cuts or jointed angle cuts.
  4. Set up the square as a saw guide for a circular saw . Position the tool with the fence resting against the edge of the board. Your guide leg should be running across the board at either a 90- or 45-degree angle, depending on the cut you need to make. Slide the saw plate flush against the outer edge of the square and push the saw along to make a neat cut from one end of the board to the other. [13]
    • Using your carpenter square as a saw guide makes it possible to get cleaner, more precise cuts than you could get by freehanding your saw. It also saves you the trouble of having to carry and configure a separate saw guide.

    Tip: Plastic squares tend to make safer saw guides than metal ones. Since they’re slightly thicker, there’s less chance of the saw blade accidentally riding up onto the square itself. [14]

    5. Advertisement


Expert Q&A

Ask a Question
200 characters left
Include your email address to get a message when this question is answered.
Submit
      Advertisement

      Video

      Tips

      • No matter how you use your carpenter square, remember the old handyman’s adage: measure twice, cut once. It won’t matter how precise your measurements are if you fail to check them before altering your materials.
        Thanks
        Helpful 5 Not Helpful 1
      • Consider keeping two squares in your tool box, one plastic and the other stainless steel. The steel square will offer unmatched durability for years of dependable use, while the plastic square will work better for sawing and quick checks, and can easily be replaced if lost.
        Thanks
        Helpful 4 Not Helpful 1
      • Once you’ve familiarized yourself with the various functions of a carpenter square, you’ll find that it’s one of the only tools you need to accurately map out square lines and angles for carpentry projects.
        Thanks
        Helpful 4 Not Helpful 3
      Submit a Tip
      All tip submissions are carefully reviewed before being published
      Name
      Please provide your name and last initial
      Submit
      Thanks for submitting a tip for review!
      Advertisement

      You Might Also Like

      How to
      Read a Ruler
      How to
      Read a Tape Measure in Inches or Centimeters
      How to
      Measure Centimeters
      How to
      Read a Vernier Caliper for Super Precise Measurements
      How to
      Measure 2/3 Cup with a 1/4 Measuring Cup
      How to
      Use a Ruler to Measure in Millimeters (Plus Estimating Lengths)
      Easy Ways to Measure Liquids When You Don’t Have a Measuring Cup
      How to
      Calibrate a Digital Scale With and Without Weights
      How to
      Calculate Angles
      How Big Is an Inch? Here's How to Measure Accurately
      How to
      Read a Caliper
      How to
      Measure Without a Ruler
      How to
      Use Calipers
      How to
      Read a Dial Indicator
      Advertisement

      Expert Interview

      Thanks for reading our article! If you'd like to learn more about using tools, check out our in-depth interview with Ryaan Tuttle .

      References

      1. ↑ https://makezine.com/2015/09/03/skill-builder-use-speed-square/
      2. ↑ https://www.youtube.com/watch?v=yPL6jOa6AH8&feature=youtu.be&t=71
      3. ↑ https://makezine.com/2015/09/03/skill-builder-use-speed-square/
      4. ↑ https://www.familyhandyman.com/tools/how-to-use-a-speed-square/
      5. ↑ https://www.nachi.org/roof-slope-pitch.htm
      6. ↑ https://www.youtube.com/watch?v=vnhsGGUfCUM&feature=youtu.be&t=37
      7. ↑ https://www.familyhandyman.com/tools/power-tools/how-to-use-a-power-planer/
      8. ↑ https://www.youtube.com/watch?v=yPL6jOa6AH8&feature=youtu.be&t=13
      9. ↑ https://www.popularmechanics.com/home/how-to/a3999/4306646/
      1. ↑ https://makezine.com/2015/09/03/skill-builder-use-speed-square/
      2. ↑ https://www.youtube.com/watch?v=yPL6jOa6AH8&feature=youtu.be&t=29
      3. ↑ https://www.popularmechanics.com/home/how-to/a3999/4306646/
      4. ↑ https://www.popularmechanics.com/home/how-to/a3999/4306646/
      5. ↑ https://www.familyhandyman.com/tools/how-to-use-a-speed-square/

      About This Article

      In other languages
      Thanks to all authors for creating a page that has been read 127,191 times.

      Reader Success Stories

      • Antonio Lemos

        Apr 4, 2022

        "It's a very precise description of what hands-on people need."
      Share your story

      Did this article help you?

      Advertisement