It happens to everyone. You thought you had a stash of zip ties (cable ties, tie wraps, whatever) in your tool bag and you just found out your all out. Sometimes you have to secure cables in a plenum environment but you don't have the plenum rated zip ties. The barrel knot will fill in nicely and you can use wire or string to tie it.
The barrel knot is the old school zip tie. This was taught to me by a Marine who had learned it by reading a WWII era field manual on cabling.
Step 1: Choose the Material for the Knot
Here I am using 24 gauge cross connect wire. You can buy a roll of it here