I thought I would share a tool I just recently purchased. And fell completely in love with. When I was doing my recent top Garden Patch, I had to piece approximately 500 half square triangles. One thing I learned from doing this pattern is to read all the way through a pattern before you do anything. The first step was to cut all of your fabrics. This pattern required you to cut larger squares and then later had you trim them down to make your triangles. If I would have noticed how many triangles I had to trim I would have cut them to the accurate sizes.
Anyway, about half way through the quilt I found this tool online. Its called the Bloc-loc ruler. I purchased it from Missouri Star Quilts. I don't think I can even describe how much I love this ruler. If you have to make a large number of half square triangles this is the ruler to have. See that line through the middle? That line is a quarter inch in size and its recessed into the ruler. Your seam line sits perfectly in there. So when you trim your block it doesn't move and the ruler doesn't slide. After you do one corner you simply slide it to the other and turn the block around. It made the process so much quicker.
Here's a video showing how it works:
Isn't it great!