Brand: SmartRacing Products
The square-section Hook Leg is the vertical piece that holds one end of the String Bar in the Smart Strings 4-Wheel Toe Alignment Kit (formerly Pegasus Part No. 3180). The string bar rests in the hook on this leg and his held firmly at the other end by the Holder Leg. This Hook Leg is Item 4 in the SmartStrings instruction sheet.
These legs (especially the hook) can get tweaked bouncing around in the trailer, but if the leg is not straight you will have a hard time repeating your set-up.
Sold individually, one used for each end of the car.