Get 20 buttons. 10 should be round and flat. 10 should be octoganal and thick. Sew one group along the long sides of the blanket and the other group along the short sides. Now in the dark, you can feel what side you have found. Take it to the next level by incorporating braille on the buttons that identify the position on the sheet. Now you know what edge and the position you have grabbed. Go another step and sew buttons on the reverse side that tell you which side is up/down. Now, in the dark, you grab an edge and know what side, where, and the orientation of your blanket. Or just duct-tape your blanket down before you fall asleep.