Push the safety pin into one of the holes in the hem tunnel.

Push the pin as far as possible, and then hold it in place through the fabric. With the other hand, bunch the hem tunnel towards the first hand.

Slide the pin into the bunched hem tunnel, and try to pinch it with the receiving hand. Now, let go of the pin with the first hand, and use this hand to pull the hem tunnel taught.

When done correctly, the pin will transfer from one hand to the next hand, slowly moving along the hem tunnel with every bunching-tautening motion.

Keep repeating this action until the pin reaches the other end of the hem tunnel. Now, pull out the pin and drawstring together.