Two people stand on opposite corners of a handkerchief They do not stretch or alter the handkerchief in any possible way How can they both stand on the handkerchief simultaneously without having a?

By laying the handkerchief across the threshold of a doorway. Have 1 person stand on the handkerchief on one side of the threshold, then close the door & have the other person stand on the the other side of the handkerchief. They will be unable to touch each other without moving the door. Unless it has a window in it.