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How to Tie A Underwriters Laboratories (UL) Knot

For decades now lamp makers and manufacturers have been tying UL knots in lamp cords just below the socket interiors. Once the socket shell and cap are closed, the UL knot is not visible. This simple and effective knot is a real safety feature for table and floor lamps. If the lamp cord is pulled, the UL knot will protect the cord from coming loose from the socket screw terminals.

This exploded lamp diagram shows the parts of a table lamp. The UL knot in the lamp cord sets between the socket cap and the socket interior.

Exploded Diagram of Table Lamp Parts

Tying a UL knot is easy. In 4 steps the knot is complete and the lamp cord is ready to be attached to the screw terminals.

Step 1: Split the wires apart


Step 2: Bend the left wire down and behind the cords.


Step 3: Pull the right cord down behind the left cord and in front of the cords.


Step 4: Continue the right cord through the left loop. Pull the knot tight.


UL knots should always be used in table and floor lamps for safety.