I bought plexiglass from the hardware store and had them cut it into different sized squares.
Or - are you talking about once the quilt top is together?
At that point, it might be too late ;)

love my 12 1/2 " square up ruler

So do you put the corner of the square ruler on the corner of your block? What if you see your block is not square? Won't whacking off the block to make it square cause your block to end up too small? I too think I need a tutorial on this subject.

I second that! Would love to see a tut

DITTO

ditto ditto

That's a really good question and the answer - as so often: It depends.

I usually measure my blocks to see what size range I am dealing with. Then I see if I can block the smaller ones to be the correct size. There is a little play allowed (if you listen to Eleanor Burns, I think she allows 1/8" which can be adjusted).

To block, I spray the block lightly with starch and/or steam press it into shape. I pin it to the ironing board and let it dry. That has never let me down, BUT I never try to "fix" large discrepancies.

When the block is too large, I see if any points will be lost if I cut it down. If I have no HSTs along the edge, I may just cut it to fit. Some blocks are easier to trim than others and a lot depends on how they would look next to the neighbor block.

So does the spray starch or sizing make the fabric in the block stretchier so you can pull it slightly into a more square shape? So if you have what looks like a slight parallogram you spray and then pull it straight and then pin it to the ironing board and let it dry into it's new (hopefully square) shape?

If it's just a matter of the block being too big you trim it off into a square, unless you have HSTs on the edge. What is an HST? If you have one of those I suppose you chuck the whole thing and just make a new block taking more care to get this one straight to start with. I sure hope I have extra fabric in the right prints if that happens.

I appreciate your help to understand this. Can I use the square up ruler to make sure my blocks are square when I cut them? I am using a 3x18" clear ruler, a cutting mat that is slightly larger, and a rotary cutter.

Check Youtube. They have lots of videos on squaring up quilt blocks.

well walmart ahs june tailor square rulers for 26 its a set of four; a 12, a 9, a 6, and a 4 inch. they do have a blue edge that adds a fourth inch to each side. so you dont have to measure for seem allowence.