Abstract: A door strap system includes a trailer that may contain cargo. The trailer has an outer wall and a rear side and the rear side is open to access an interior of the trailer. A door is slidably coupled to the trailer and the door is positionable between an open position and a closed position. A lift truck is selectively driven through the rear side of the trailer when the lift truck loads and unloads the trailer. A strap is coupled to the door thereby facilitating the door to be pulled downwardly into the closed position. A retention unit is coupled to the strap and the retention unit selectively engages the outer wall of the trailer such that the lift truck is inhibited from contacting the strap when the lift truck is driven through the rear side.