I love your colors, lawsonmugs!

Yes, I had this problem, too. I think about half of them came out right, and the other half were just shy of the width either at the top or the bottom. I wondered if it might be because I was cutting four layers at a time. It seems these have to be really exact with the placement of the side pieces, and I could see that my notch had quite a bit of variation to it. So I will have to do some fudging when it comes time to incorporate these units.

I had the overwhelming urge to see what the quilt will look like in the alternate colorway I was considering before being seduced by Bonnie's photos of lavender fields and sunsets. So I have been working this week on cutting a second version of the mystery units. Clue #1 will be scrappy, and the rest will be constants. I think I should get to my original clue #5s today or tomorrow.

700 1/2 square blocks, That was my first mystery, I must have made 1000 to get 700 keepers :)

Pam I found with the trirex and companion rulers I need to see the sliverest of slivers of the fabric on the left side of the measurement. I hope that makes sense.

Pam - It's been a while since I used the Tri-Rec, but I think I had to keep moving my needle over to get the correct finished size. I am using the Accu Quilt for this mystery and even with that, I am moving the needle over more than I normally would. I am sewing on my HV Topaz 50 and using a quilting foot. With the 4-patch, I moved the needle over 1.8. And with Clue 2 and 4, I moved the needle to 2.5.

Maybe it's just something with the shape of the pieces. ?

I was using my Accuquilt cutter then gave up when I kept getting them too small. So yes, I am having the same problem and am now using the Tri Recs and cutting them larger and then trimming them down. It is saving me a lot of frustration.

I normally have the same problem with blocks being slightly different. I even have a 1/4" pressure foot, so you'd think they'd all be the same.

For this mystery quilt (since Bonnie said measurements needed to be exact), I'm making all the blocks a teensy bit larger then trimming down so they all end up the exact same size. I don't have the tri-rec ruler, but my V-block ruler does make the blocks slightly larger for trimming down.

I used the Tri-Recs rulers. I cut from four strips stacked. I used a scant seam. I felt my end result was suitable.

If yours are just slightly too small, you might consider using starch when ironing, sometimes that helps.

Or, if the size is too big or too small at the top or bottom of the seam, try re-ironing. If you are cutting from WOF strips, or anyway, from strips that are straight of grain, then the seam allowance that you'll sew on both triangle pieces are on the bias. How you iron a bias seam can make a big difference in size-- because you can stretch it one way or another, and sort of 'heat-set' it wacky with the iron.

And if your going to use starch when ironing, make sure you starch the fabric before cutting it. Ask me how I know...

Thank you for all the input, ladies! My problem could be any of these things mentioned. I hope to be able to work on this again today.

What happened? I pretty much just starch my blocks as needed.