Explain you forgot to bring any rope with you, so a little magic may help!

Freely display a large blackboard showing it blank front and back. Write the word R O P E on the empty blackboard with white chalk.

You'll need more than the word ROPE to perform magic!! Grab hold of the word ROPE written in chalk and pull it right off the blackboard!

It has turned into an actual piece of ROPE! The blackboard is empty! The word ROPE is now written in black channel!