Snowball and stitch-and-flip corners

Snowball block size chart

For the classic snowball, with corners a third of the block’s side. For other corners, use the calculator: the rule is the same.

How it’s worked out

A snowball corner, also called a stitch-and-flip corner, is a small square sewn across the corner of a bigger one. Sew from corner to corner of the small square, trim the extra ¼″ beyond the seam, and press it out: the corner becomes a triangle. Nothing is cut on the bias, so it’s the most forgiving triangle there is.

Because both pieces are squares, both are cut the finished size and ½″, like any square. Measure the corner’s finished size along the block’s edge: where the triangle’s short side meets it.

Quarter Inch’s cutting chart cuts the library’s 12″ Snowball the same way: 4 squares 4½″ of Dark (stitch and flip: the corners) and 1 square 12½″ of Light.

Bonus half-square triangles

The corners you trim off are two triangles already right sides together. Before you trim, sew a second line ½″ outside the first, then cut between the two lines. Press the offcut open: a small half-square triangle. For 2″ corners, trim them to 1¾″.

Why that size: the cut is ¼″ outside the seam, so the offcut’s short sides are the corner square less ¼″ × √2. Sewn ¼″ from the long side, a triangle loses ⅜″ as a half-square triangle does, and that comes to 1.771″. Down to the ⅛″ you can trim to: 1¾″.

Snowball corners or half-square triangles?

• Snowball corners are quicker and nothing stretches. They use more fabric: half of each corner square is cut away, unless you keep the bonus triangles.
• Half-square triangles use less fabric. For a 2″ triangle in the corner, a 2⅞″ square makes two. See half-square triangles.
• On a rectangle, the same sewing makes flying geese: a 4½″ × 2½″ rectangle with two 2½″ squares. See flying geese.