A cable tie (also known as a zip tie) is a type of fastener for holding items together, particularly electrical cables and wires. Most cable tie consists of a flexible nylon tape with an integrated gear rack on one end and a small opening with a ratchet on the other. The gear rack is inserted into the opening and past the ratchet which prevents it from being able to be pulled back out.
Cable ties are sometimes used as a restraint, since they can usually only be pulled tighter once they're tightened. Usually used tying the wrists or thumbs together.