How do you square? Do you simply use the grid on your cutting mat to see if it is square and then hack it off right there ?

squaring to correct size is very important. just make sure you don't make them smaller than required though.
and hst's should be squared/trimmed by placing the 45 degree line on your ruler on the seam line. also very important.

Being an 1/4" off here and there, can come around and bite you later on. If 12 blocks are 1/4" bigger than they should be, the row will be 3" too long. So your measurements for the borders in the patterns would be inaccurate. If your borders are pieced, this will make a major problem for you, and that is a lot of extra fabric to try and ease in.
The more pieces going into a block, the more opportunity for variances, and the more important it is to check for accuracy. A 12" block with 9 pieces won't vary as much as a 12" block with 36. If you find your piecing and cutting is fairly accurate, you may just want to spot check your work.

Using different brands of rulers, or the grid on your mat can make for variances too. There is a difference in some brands of rulers :wink: You may want to compare yours, as sometimes that may be what is causing a variance in your piecing/cutting.

I tossed out one ruler because when I cut out 4 in blocks, they were all just off far enough, that a scant 1/4" seam still made them too short when pieced into a 9 patch. I cut them with different ruler and they were spot on. I then double checked them with another ruler and got the same perfect measurement. Had I of used my mat for part of this process, I would have ended up with a slightly different measurement also.... I wondered if the machine in the factory was a bit off and in need of an adjustment that day :roll: and that is what caused that ruler to be off...

The more time you invest in prep work, the better your final product will be. If you square them now, the assembly will go much smoother. Trust me on this - it's a lesson I learned the hard way.

I square as I go. I use the ruler to square up. Some people use the mat lines and ruler.

All I can say is that every time I don't square as I go....I wish I had! lol

I square as I work. I makes blocks go together much easier. The end result is much better.

It's weird - when I sew pieces together on the straight of grain, the units end up really close to the size I am expecting them to be.

When I sew triangles together on the bias side- using what I think is the same seam allowance, they squares end up skimpy.

I've also resorted to making the HSTs slightly oversize and trimming down.

It may waste an 1/8 inch of fabric on two sides of the square, but it sure saves a lot on aggravation.

I try to square as I go.

I square up as I go. Every time I sew a section of the block together. Especially the 1/2 square triangles. ( And always make them slightly larger to allow for squaring.) And after the block is finished, I press and square up the block. All the blocks have to be the same size and allowing for the 1/4 inch seam allowance. A 12 inch finished block will be 12 1/2 inch before sewing the rows together.