Crispy_Frog, The blocks are 11" raw, will be 10 1/2" finished size. A lot of people use a little waste piece of fabric to start chain piecing-- that way when you start the triangle seam for the HST it will follow the little piece of fabric, and you just continue chain piecing all your units. Some people don't like using a little piece of fabric and go with the 'leader/ender' idea, where the first piece you sew is something you will use later. So, if you can sew easily two squares together, for example, then you could use that to start sewing, and after that first unit, start doing your triangles. Another thing you can do is tightly hold your top and bobbin threads. Sometimes it is the thread going down into the feed dogs that leads the point of the triangle down into there along with it.