After dozens and probably hundreds of times pulling my power tool plug out of my extension cord receptacle, I finally broke down and did something about it.
This project required only a scrap of 1 1/2" PVC pipe. For tools,I used a table saw, a miter saw, a drill with a 3/8" inch bit and a saber saw.
Step 1: Cut the Pipe
Starting with a scrap of pipe. Cut it about three inches longer than your plug and recepticle combined.
Step 2: Cut the Pipe, Continued
Cut two slots about 8 - 10 inches long, opposite each other, lengthwise from one end of the pipe.
Step 3: Nearly Done Already
Cut each end of one piece of the pipe at a 45 degree angle. Sand the burrs off.
Drill a 3/8" (or as needed) hole near each end. Using the sabre saw, cut a slot for the wire at each end as shown, making it slightly keyhole shaped. (Slightly wider at the end than at the hole.)
Step 4: Finish It Up
Again, sand off the burrs.
To use, position the plug and receptacle in the middle of the lock then push the wire through the slot into the hole. If you are careful keyholeing the slot, the wires will stay in place no matter how many times you tug on the tool.