1. Length

Measure from the inside of the bulkhead to the inside of the tailgate. 

Note: For Chest style tool boxes make sure to also measure from the inside of the bulkhead to the wheel well. This will insure that the tool box will fit. If the wheel well is too close we recommend purchasing a tool box with a pass through notch. 

Measure from the inside of the rail to the other side of the inside of the rail. 

Note: Some truck beds are square and some taper which means they can be shorter in the front and wider in the back or vice versa. Each brand, model and year can be different. 

Note: When mounting the L-series saddle tool box make sure there is 1.5'' of space on the rail for the tool box to be securely mounted on the truck!  

Measure from bottom of bed to the top of the rail. 

Note: When purchasing a McWelco Yoke rack make sure to measure from the top of the rail to the top of the cab to make sure the hight clearance will work for your truck.