It's probably destined for the land fill. I suppose you have already used up both sides. You might try soaking it in water and see what happens.

bkay

BOTH sides? I never knew............

Any suggestions what type of marker to use for drawing meaurment lines on the back side?

Actually you should use your ruler for measurements not the lines on the mat. The lines on the mat are not always correct.

My mat has lines and numbers on both sides. One side has a dark background and one side has a light background.

bkay

Have you tried lightly it?