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Square and Compass Quilt Block Pattern

Author Photo
By Rebecca Martin | Jun 27, 2019

Photo by Amanda Barnwell

Depending on who designed them and how and where they were modified over time, quilt patterns can have different names. This pattern is called Square and Compass in The Collector’s Dictionary of Quilt Names & Patterns, but that book also pictures another block by the same name that doesn’t look at all like this one! We may never know why these two dissimilar patterns share a name.

These instructions are for a finished 12-inch-square block. Measurements for each piece include a 1/4-inch seam allowance. The total number of blocks you’ll need to make a bed quilt will depend on how many borders you add (and their width), how far you want the quilt to extend over the edges of the mattress, and whether you frame each block with fabric strips in a style known as “lattice.” Typically, a quilt made of 30 12-inch blocks with no lattice will fit a queen-size bed with a drop of 10 inches over the edges of the mattress.

Cut the Pieces

The Square and Compass block design is made up of 32 triangular pieces of the same size. The pieces are arranged in four rows of 8 pieces each. For every 12-inch block, you’ll need 16 “A” pieces and 16 “B” pieces. In the photo of the finished block, “A” is a red print and “B” is plain beige.

“A” and “B” are the same dimensions. Although you’ll have to cut a lot of pieces to assemble a block, those pieces are all the same size, so you’ll be able to batch-cut them fairly quickly. To batch-cut the pieces, start with a strip of fabric measuring 3-7/8 inches wide and about 32 inches long. Beginning at one end of the strip, making sure its edges are true, cut off 3 7⁄8-inch squares. When you’re finished with the strip, you should have 8 squares. Take up each square, and mark a diagonal line from corner to corner. Cut along the line to produce 16 triangular pieces in the first color. Repeat with the second color of fabric.

If you’d prefer not to batch-cut, you can create a cardboard or plastic template with the triangle’s legs on either side of the right angle measuring 3 7⁄8 inches, and trace and cut each triangle individually. Remember to cut 16 triangles for “A” and another 16 for “B.”

Illustration by Amanda Barnwell

Assemble the Blocks

Step 1: Make squares. Sew a patterned “A” triangle to a plain “B” triangle along the long edge, being careful, as triangles are cut on the bias and will easily stretch out of shape. Repeat with remaining “A” and “B” pieces. Press seams open. You should have 16 squares.

Step 2. Arrange the squares. Lay out the 16 squares in the pattern, as pictured at the top of Page 85. Note that there are four rows, which we’ve labeled Units 1 through 4.

Step 3. Assemble the rows. Sew together the four squares that make up Unit 1. Press seams to the outside.

This pattern is complicated, so it’s helpful to pin the pieces together along the seam allowance, and then double-check the position of the triangles before you sew. If you make a mistake, remove the stitches with a seam ripper, reposition the triangles, and sew again.

Illustration by Amanda Barnwell

After Unit 1 is sewn together in a row with the triangles correctly positioned, sew together the individual squares that make up Units 2, 3, and 4 (see illustration above).

Step 4. Complete the block. Line up the seams of the squares on the assembled rows Units 1 through 4 (see illustration at right), pin, and sew the rows together. Press seams to the outside.

Step 5. Make remaining blocks. Repeat Steps 1 through 4 to create the desired number of quilt blocks for your project.

Make the Quilt Top

Now you’re ready to sew the blocks together to make a quilt top. You can either separate the blocks with lattice strips that are several inches wide, which is helpful for beginners because lattice will disguise mismatched seams where points meet on the blocks, or you can leave out the lattice strips.

First, mark 1/4-inch seam allowances on the wrong sides of the blocks. If adding lattice, measure and cut strips — usually 2 to 4 inches wide — in a contrasting color, and mark seam allowances on them. For a different effect, you can add a contrasting square at the point where the horizontal and vertical lattice strips meet. Sew the blocks and lattice together to assemble the quilt top.

Borders are another option that will provide a quilt with a finished look, and they’ll also increase the size of the quilt top to drape over the sides of your bed. You can add a single wide border or multiple borders of varying widths. Mark the borders with a 1⁄4-inch seam allowance before sewing them to the quilt top.

The next step is to assemble the layers of quilt top, batting, and backing. Start by smoothing them out on a flat surface, taking care not to introduce any wrinkles as you work, layering them in this order: first the backing (right-side-down), which should be larger than the top by several inches; then the batting (an ultra-thin polyester quilt batting is the easiest to quilt through); and finally the pieced quilt top (right-side-up). Keep the layers together and lying flat by either basting through all layers or pinning them with large safety pins. Finish by quilting through all the layers, or by sending the assemblage to your favorite local quilter-for-hire.

Illustration by Amanda Barnwell


As a Capper’s Farmer editor, Rebecca Martin gets plenty of opportunities to share her experiences of cooking, crafting, gardening, and memories of growing up on a farm.

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