Block #3 –
Shoo Fly – Quilt Assembly Tricks – The Half-Square Triangle (HST)
What is a HST?
Half
square triangle units are possibly the most commonly used patchwork component.
Sometimes abbreviated as HST or called a triangle square, the units are squares
that are composed of two triangles. Each triangle occupies half of the square's
space, leading to the name half square triangle unit.
Why Learn this Technique?
You can
sew two triangles together to create a HST unit, but it's easier, and often
more accurate to quick piece them, since it eliminates the need to handle the
stretchy bias edges of individual triangles.
Is this Lunch or Quilting?
One way
to piece HSTs is the easy sandwich method, where two squares of fabric are sewn
together along the diagonal and then cut apart to create two identical HSTs.
The
sandwich method is a perfect technique to use when you're making a scrap quilt
or need a few HST units in specific color combos -- it helps you make great use
of fabric scraps or small yardages. However, I use it even when I'm making lots
and lots of identical units.
Cut the Squares and Mark the Diagonals
1.Use the
square size called for in your pattern. If you are drafting your own pattern,
cut squares that are 7/8" larger than the finished size of the units
(unless you want to make them oversize and then cut back for complete accuracy,
see page 5).
2.Use a
pencil or permanent marker to draw a diagonal line (from one corner to the
opposite corner) on the reverse side of the lightest square.
3.If you
do not have a quarter-inch presser foot, draw two more lines, each one
1/4" from the original diagonal line (extra lines not shown)
4.Pair
the marked square with the same size darker square, edges matched and right
sides together.
5.Sew two
seams, each one 1/4" from the marked center line (measure and draw seam
lines before sewing if you do not have a quarter-inch presser foot to guide
you).
6.Use
scissors or rotary cutting equipment to cut through both layers of the square
on the marked center diagonal.
Press the
Half Square Triangle Units
1.Place
the cut units on your ironing board, the darkest fabric up. Press a medium iron
directly onto the units to set the seams.
2.Open up
one unit and carefully move the iron into the diagonal that separates the dark
half from the light half. Let the weight and heat of the iron press the unit,
because ironing with vigorous back and forth movements will stretch it out of
shape. Repeat to press the second unit.
3.Trim
the "dog ears" from the ends of seam allowances. Measure the units.
If they are too small, make sure they were pressed adequately. If squares are
still slightly small, try sewing the next squares together with seams that are
slightly less than 1/4" from the marked center line.
4.Now you
have two identical half square triangle units that should measure 1/2"
wider and taller than its finished size. The straight grain of each triangle
lies along the outer edges of the square.
