Abstract: On July 20, 2007, Employee #1, a 46-yr-old male, a maintenance mechanic, in Avenal, CA, was disconnecting a utility trailer carrying welding equipment from its tow vehicle when the top wind pivoting tongue jack with cast wheel failed to support the trailer tongue. Employee #1 reported he rotated the tongue jack to its vertical position, checked for engagement of the plunger pin and cranked the jack down until the hitch was clear of the tow ball. As the tow vehicle, driven by another employee, pulled away the jack kicked out causing the trailer tongue to fall. The trailer's frame struck Employee #1 at the anterior surface of the right tibia and avulsing by scrapping action just above the ankle and pinned him under the trailer tongue. The injury resulted in nerve damage and subsequent surgical treatment. The other employee used a pipe to extricate Employee #1 from under the trailer that had 450 lbs of tongue weight. A physical inspection of the tongue jack revealed several defects that would affect the ability of the jack to support the load. Significant wear was observed on the plunger pin, the mounting bracket, and the jack bracket. In addition the trailer was parked on a rough concrete surface that was sloped at 0.25 inch per foot and the wheels were not chalked. Root cause analysis concluded that the jack failed to support load based on excessive wear on the pivot locking mechanism, due to failure to secure movement with chalks or other wheel locking devices.