These are probably the most commonly found units in patchwork and, as their name suggest, they are a square consisting of two triangles.

We will show you two quick-piecing methods here, the first makes two units at a time using squares; the second uses strips to make several units. The key measurement to remember for these units is 7/8 - this the added seam allowance to the required finished size. So if your finished half-square triangle (hst) is 3 inches then you will need to cut your squares or strips 3 7/8 inches.

To make two units cut a square of each of your fabrics (these are orange and black in our example) that is 7/8 inch larger than your finished unit size.

draw diagonalMark a diagonal on the wrong side of the lighter fabric (it is easier to see usually). You can use any straight edge for this - in the photo it is an emery stick as this grips onto the fabric and stops everything sliding about.




stitch either sideStitch 1/4 inch either side of this marked diagonal.




cut diagonalCut along the marked diagonal line.




hst unitsPress the seams to the darker fabric - you should have two half-square triangle units.





Half-Square Triangle Units from strips

cut strip

second stripCut a strip from each of your two fabrics, 7/8 inch wider than the finished size of your hst units.





mark strip


On the wrong side of the lighter strip mark squares. If your strip is 3 7/8 inches wide then mark lines at 3 7/8 inch intervals.

Mark a diagonal on each square - in such a way that the diagonals form a continuous line along the strip.




stitch secondPlace the strips right sides together and stitch either side of these diagonals - you should be able to do it in two long runs, pivoting at each turn.

Press the strips once the stitching is complete to set the stitches in the fabric.



cu tsquares

Cut the strip into squares along the drawn lines.




cut diagonal


Cut the squares in half along the drawn diagonals.




press squarehst units completed


Press to the darker fabric to complete your Half-Square Triangle units.