If a doorknob doesn't have visible screws on either side, you can still remove the doorknob by locating the detent hole or pin. This small hole is typically on the side of the doorknob and can be used to release the door handle by inserting a small screwdriver or the end of an Allen wrench into the hole and applying pressure. Just make sure to find and remove the set screw on the bottom of the doorknob before pushing down on the pin, otherwise the doorknob will remain in place.