Jenny apologised!

[Lisapc]

I do it all ways. Mostly I use the mat for that first squaring up cut. Then I measure and line up my ruler and since it matches with the lines on the mat I guess I use both at once. The only time I don't is when I am squaring a block. If I have the right sized square I use that. If I don't I use masking tape to mark the correct size of the block and then just line it up with the lines of the ruler and trim to size.

[Judy, USMC]

...... I measure and line up my ruler and since it matches with the lines on the mat I guess I use both at once.

That's how I do it too!