I should know better than to "ass-ume" something without double-checking. I checked to make sure all my 60-degree rulers were the same but I didn't think to check that Tri-ruler.
And I'm sorry that I've led you astray.
If I tell you that I have a solution, will you forgive me?
This will work using any regular ruler - a 6" x 12", 6" x 24", or a square ruler - with 60-degree lines on it. When I first wrote the pattern, I wasn't sure how it would be lined up consistently. But necessity meant I had to figure something else out so I went looking for another solution... and I found one. And as luck would have it, it's one that's pretty easily done.
Just so you know, most of the 60-degree triangle rulers have a flat tip at the top. That means that they aren't automatically interchangeable with simply cutting 60-degree triangles using the lines on a regular ruler. That flat tip at the top changes the finished "height" of the triangle by 1/4". Been there, learned that... the hard way.
But let me get back to Hook... as luck would have it, the measurement of the base of my triangles is exactly 4". Whew.
This is what you need to do...
Make a strip set according to the pattern - yes, this one is a little shorter.
Press the seams open. Shave/trim the top and bottom edges straight. Start with the background rectangle on the left side.
Align the 2" line of a ruler on the seam as shown. Use a marking pen to mark the 2" points on both sides of the seam line - the lines will be at 0" and 4".
This shows four (4) marks - these are the marks for 2 triangles. The two marks in the 2nd background piece are approximately 1/8" apart. The first mark - the one on the left side - is for the first triangle, the second mark is for the second triangle. With your strip sets, you'll make three sets of marks - six total - on the first side of the strip set. Then you'll make two sets of marks - four total - on the second side of the strip set.
Align the 60-degree line on the top edge of the strip set and cut from the first mark to the seam line.
Note: The 60-degree lines on your ruler will likely be in a different place than they are on my ruler so don't worry if your alignment looks different. As long as the angle is 60-degrees, this works.
Align the 60-degree line on the bottom edge of the strip set and cut from the second mark to the seam line. Repeat to cut two more triangles.
As before, mark the points 2" on either side of the seam line.
Serendipity. There will be enough remaining on the other side to provide you with a straight edge to align the ruler. As before, align the 60-degree line with the top edge of the strip and cut from the mark to the seam line. Repeat to cut the other side by aligning the 60-degree line with the bottom edge.
The triangle cut from the leftover pieces is the same - use the ruler to mark points 2" on either side of the seam line.
And trim the sixth triangle using the 60-degree lines.
For the alternating triangles - background or a different fabric - there are two ways to do this.
If you haven't already cut the strips for the setting triangles and pieces... Cut those strips at 3 1/2" wide. Then just cut triangles using the 60" line going tip to tip - there won't be a flat tip.
But if you've already cut your strips...
Measure 4" from the cut/clean corner edge of the fabric. Using the 60-degree line of the ruler, cut from the mark to the top of the strip. Then go back and cut the opposite side from the cut/clean corner of the strip. That will yield a 60-degree triangle the same size as the pieced-triangles cut above - except that it will have a flat tip.
Voila! Repeat on the top edge - measure 4" from the angled tip of the fabric. Align the ruler on the 60-degree line and cut from the 4" mark to the bottom edge of the fabric. It will make sense as you start cutting - you'll see.
Voila... Part Deux. This is a background triangle on top of a pieced triangle I cut above. Nope, don't worry about cutting that tip. You'll do it eventually - probably - cut it isn't necessary yet.
And there you have it.
I know you can do this. As always, if I can do it, so can you. Really. I don't have any magic powers or crazy-mad-skillz. As if!?
If you don't believe me, ask Rosie.