Quiltmaking 101 -- trimming your quilt

First, a word about square corners.  Traditionally, quilts have them, or are supposed to have them.  We think of quilts as rectangles, which makes sense with functional pieces, because beds are rectangular, and rectangular quilts will cover them and hang parallel to the floor.  But even on a bed, a slightly non-rectangular quilt will not cause the world to end.  A close look at any antique quilt will prove that our sainted foremothers didn't always get the corners perfect (no wonder when you think of the tools they had), but the quilts are just as precious.

When a quilt is intended for the wall, there's even less reason why the corners have to be perfectly square.  Square corners aren't bad, they're just optional.  In most cases you will want your corners to be square, and that's fine.  But if they end up a little off, either inadvertently or deliberately, that's OK.

How you trim a quilt depends on your equipment, specifically how many cutting mats you own, and whether they can be fit together in an expanse larger than your quilt.

If your plastic ruler isn't long enough to cut the entire quilt, use a yardstick.  I own a 72-inch metal ruler that is good for trimming very large quilts.  A friend of mine splurged and bought four 72-inch rulers!  She can lay all four onto the quilt to establish the four edges, and look carefully before she cuts anything, just as you might decide where to crop a photo by placing strips of paper over the edges.

Helpful hint: Long rulers can slip while you're cutting.  If you don't have a helper to hold the other end of the ruler, and if your cutting surface has an overhanging edge, maybe you can use a clamp.

If your quilt is small enough to fit on your cutting mat (or multiple mats pushed together), trimming is easy.  Arrange it on the mat so the top edge aligns with one of the gridlines. You may want to weight down the quilt so it doesn't slip around.  Put your ruler across the quilt, align it with the gridline, and slice the top edge straight across with the rotary cutter.

Without moving the quilt, shift your ruler to one of the other edges and align it with the gridlines on the mat.  (Or if your quilt isn't going to be exactly square, place it wherever the edge should be.)  Slice that edge straight across.  Repeat with the other two edges.  You may want to carefully rotate the entire cutting mat, with the quilt on it, to bring the edges closer to you.

If your quilt is larger than your mat(s), it's trickier to cut the edges.  You'll have to shift the quilt in mid-edge, or perhaps weight down the bulk of the quilt and shift the mat under it. You'll have to make sure that your rotary cutter doesn't go off the edge of the mat and slice up your tabletop, your carpet or your floor.  Take time to think before you cut.

Cutting is easier if your ruler is longer than the quilt.  If it's not, you'll have to shift the ruler as well as the mat.  It's certainly possible to trim a quilt with a short ruler and a small cutting mat, but each shift is tedious as you check your accuracy and check again before cutting.  You can see why quilters very quickly tell Santa they want a larger cutting mat (or maybe two or three) and a longer ruler.  Although this equipment is pricey, you'll never regret its purchase, because it changes trimming from a difficult task into a snap.

The first step is always to establish a straight line across the top of your quilt, because that's the edge people look at first when they decide whether something seems crooked.  Then slice the top edge of your quilt along that line, moving the quilt or your mat if necessary.

After you've cut the top edge of your quilt, align the cut edge with the gridline of your cutting mat (in the photo, the top edge is at the right).  Here two cutting mats have been pushed together to give a long surface to cut the second side.  Line up your ruler with the gridline and cut.

If you have an opaque ruler, line up the bottom edge with the gridlines on the mat.

If you have a transparent ruler, you can line up any of its lines with the gridlines on the mat.  Transparent rulers are helpful because you can see what's underneath, but they're usually shorter than all but the smallest quilts.

With larger quilts it may be harder to establish a square corner, because the gridlines on your cutting mat are hidden underneath the quilt.  Here's what to do:

Arrange the quilt on the cutting mat so as much as possible of the side you want to cut now is over a mat.  Take a large cutting square, cutting mat or piece of board -- anything you know has a right angle at the corner -- and place it on the quilt, aligning it with the cut edge.  Place the corner of the square piece exactly where you want the corner of the quilt to be.  Use the biggest such device that you own; the farther away from the corner you can establish your right angle, the more accurate your cutting will be.

Hold the square carefully in place while you put your ruler along the edge of the square, butting it up close to the edge of the plastic.  Very carefully remove the square, without moving the ruler, and trim the quilt, moving the quilt or the mat as needed.

Now go back and trim the other side edge of the quilt the same way, starting with the top edge and establishing a square corner.  Leave the bottom edge for last .

So let's say you try to make square corners, and you measure and cut carefully but you work your way around and the fourth corner isn't right.  Something has slipped a bit somewhere along the way as you picked up and set down your ruler, or as you marked, or as you shifted the quilt on the cutting mat, or as you moved around and accidentally nudged the quilt out of place.  So your task now is to come up with the best solution.

Usually I adjust the slant of the bottom edge of the quilt to split the difference. But that's not the only solution.  You can just ignore the difference, allowing one of the corners to be not-square.  Or you can exaggerate the difference, and pull one of the sides out even more so the not-square looks deliberate rather than accidental.

Sometimes your quilt has gotten misshaped in the course of being pieced and quilted, and you find yourself in a similar quandary.  Maybe one corner has pulled in a good bit because you quilted it more densely, and the only way to cut the quilt perfectly square is to crop in and lose a whole lot of beautifully pieced, beautifully quilted real estate -- or even worse, lose an essential part of your design.  Instead, you might want to have deliberately not-square corners so you don't have to cut off your hard-won handwork.

In any case, this is not the end of the world.  Your rotary cutter is meant to cut fabrics, not your wrists.