The blue painter's tape is the best! Yes this is an old trick quilter's have used a long time. You can also use the big office clips too if your table is skinny enough that you are working on. I am glad you found it out, that is ging to help you tremendously keeping the bottom straight. There is a book called, Every Trick in the Book. That has tons of tricks like this to help you to learn these things. I don't think it is very expensive and well worth the few dollars you will spend. I saw it on e bay recently, used, for cheap.