Sequence for Sewing a useful basic quilt block

Easy and fast to make for quick quilts

The "half-split/half-square triangle block"

See the beginning of this article here.

See 10 sample color quilt top layouts here.

And here are some blank quilt top layouts to color in.

See more detail notes below this table and a link to a Print version page.


A. Take the two larger squares of fabric. 

B. Put them right sides together. Draw a diagonal line on the back of one - or iron a fold diagonally to mark it.

C. Sew seam 1/4" away on each side of the line. Cut on the center line and press open to form two of the half square triangle blocks as seen on right of C.

D. Take one of the half square triangles blocks from C. and put it right side together with a plain smaller block (shown here in green).

E. Draw a diagonal line (or press it in) on the "green" square. Lay it across the sewn seam in the half-square triangle block as shown in E. Stitch 1/4" away from the center line. Cut and press

F. You will now have 2 half-split/half-square triangle blocks which are mirror images.

G. Make 2 pairs of A-F and sew them together to form Block H.

(or use them in other ways)


1. Your starting squares in A should be about 2" larger than the sewn units you finish in part F. The "green" square in part D should be about 1" larger than the units in part F. Make one sample pair first to test your seams and sizing. Thus if you want 4" finished sewn size units - make the first pair of fabric squares each 6" and the second "green" square in D at 5". Your final block shown in H will then be a 12" block sewn size.

If you want to make a 8" finished "F" sewn unit you will cut your A squares 10" and your second square 9". The finished "H" unit will thus be 16".

2. After you make two pairs of blocks as shown in G, you don't have to trim them too carefully at this point. Assemble the 4-units as in G, matching the seams and then trim the outer edges of that block to the desired size for your quilt. Remember to leave the 1/4" seam allowance on this "H" unit.

3. After you decide on a size for your blocks - cut a stack of squares in the two sizes you need and do chain assembly line type sewing and you'll have enough blocks for a quilt in no time!

4. But - remember - if you are making a quilt all from these blocks or from these blocks and plain fabric squares there is NO REASON you have to make them to a specific 6" or 6.5" or 7" size. As long as they are all the same and fit together no one is ever going to quiz you on what size your quilt blocks were precisely! If they all come out as 6.755" ... so what? As long as they sew together nicely - you have a quilt!

See 10 sample color quilt top layouts here - there are many ways to use this block. Put up a flannel design wall to experiment before deciding how to sew them. Try using some fun novelty fabrics with solids or stripes or polka dots for a fun quilt. There are 3 possible blank arrangements here to print out and color in.

 If you do something with this Half-split/half-square block and you'd like to share your quilt - send a photo or a scan for the Gallery? Email them to: quilting -at -

See a variety of sample borders made from this same block. 


Susan Druding

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