Wheel Chocks
OSHA Wheel Chock Placement on Trailers & Slopes
Cojo
May 7, 2026
6 min read
OSHA 29 CFR 1910.178(k)(1) places wheel chocks "under the rear wheels" of a parked highway truck during forklift loading. On a typical Class 8 trailer that means at the rearmost tandem-axle pair, with one chock in front of the tire and one chock behind, against the same tire. The pair-of-chocks rule prevents tire roll in either direction. On slopes, a single chock on the downhill side of one rear tire is acceptable when correctly sized; for slopes above 6 percent both sides should be chocked.
The OSHA rule names "the rear wheels" of the truck. On a single-axle trailer that is the one rear axle. On a tandem-axle Class 8 trailer (the most common configuration in U.S. industrial dock work) that is the rearmost axle of the tandem pair. The chocks go against the tires of that rearmost axle, not the forward axle of the tandem pair.
The reason: trailer load shift during forklift loading transmits roll force to the rearmost contact point. Chocks at the forward tandem-axle position can be bypassed if the load shifts in a way that lifts the forward axle and pivots the trailer around the rear axle. Rearmost-axle chocking is the OSHA-citation-safe placement.
The pair-of-chocks method places two chocks against one rearmost tire. One chock contacts the tire's forward face; one chock contacts the tire's rearward face. The tire is locked between the two chocks against forward and rearward roll regardless of which direction load shifts the trailer.
OSHA 29 CFR 1910.178(k)(1) uses "wheel chocks" in the plural specifically to invoke the pair rule. A single chock at a flat-ground dock position is a citation finding even when the parking brake is set.
The U.S. Department of Transportation's 49 CFR 392.20 reaches the same conclusion from the driver-side. The driver leaving a parked CMV must "set the parking brake, chock the wheels," and the chocking practice that satisfies the standard is the pair-of-chocks placement against the rear tires.
Six steps cover OSHA-compliant tandem-axle trailer chocking. The sequence below assumes the trailer is parked at a loading dock on flat ground. Slope adjustments are covered in the next section.
Before approaching the trailer, wait for the driver to set the parking brake and shut the engine. Visual confirmation: the brake-set indicator light or the hand-valve handle position. Approaching the trailer before the brake is set risks roll if the driver's foot slips off the service brake.
Walk to the rear of the trailer along the cab side, not through the gap between the trailer and the dock. The trailer-to-dock space is the highest-risk pinch point at any dock; never approach a chock placement through that gap.
On a typical Class 8 trailer the tandem-axle pair sits within the last 8 to 12 feet of trailer length. The rearmost axle is the one closest to the rear bumper of the trailer. Chocks go against the tires of that rearmost axle.
Set the first chock on the ground with its angled face pointing toward the tire. Slide the chock against the tire so the angled face contacts the tire tread along its full width. Push firmly with a gloved hand or the toe of a steel-toed boot to confirm tire contact.
Move to the back of the same tire and place the second chock with its angled face contacting the tire's rearward face. Same contact verification.
Loading-dock operations should not proceed until the dock operator signals "cleared" to the forklift operator inside the trailer. The signal pattern depends on the site. The U.S. Occupational Safety and Health Administration's general-duty clause requires a documented procedure for the cleared signal.
Slope chocking changes the procedure in two ways. First, chock placement priority shifts to the downhill side. Second, chock size scales with slope angle and vehicle weight.
The chock must be on the downhill side of the rearmost tire. Gravity drives roll in the downhill direction; the chock backs up the parking brake's primary uphill restraint. A single chock on the uphill side of a slope-parked trailer does not prevent roll and is a citation finding.
For slopes above 6 percent, place chocks on both sides of the rearmost tire. The downhill chock backs up gravity-direction roll; the uphill chock prevents inadvertent roll if the load shifts and the parking brake fails simultaneously.
| Slope | Vehicle Class | Recommended Chock |
|---|---|---|
| 0 to 3 percent | Class 8 trailer | 12-inch heavy-duty rubber, pair |
| 3 to 6 percent | Class 8 trailer | 15-inch heavy-duty rubber or urethane, pair |
| 6 to 10 percent | Class 8 trailer | 18-inch heavy-duty rubber or urethane, both sides of tire |
| Over 10 percent | Any class | Two chocks on downhill side, plus brake-and-engine-on transmission engagement |
A trailer detached from its tractor is at higher rollaway risk than a trailer-tractor combination because the detached trailer relies entirely on its parking brake and any chock-and-jack support. OSHA 29 CFR 1910.178(k)(2) adds the requirement that fixed jacks must be placed under detached trailers to prevent landing-gear collapse during forklift loading.
The chock placement procedure stays the same: pair-of-chocks against one rearmost tire, downhill priority on slopes. The added control is the fixed jack at the front of the trailer to support against landing-gear failure.
For the tandem-axle and detached-trailer use cases see our trailer wheel chocks selection guide for material and sizing detail.
Cojo's industrial-customer dock walks identify five recurring placement errors:
Each error is preventable through procedure documentation and quarterly compliance walks. The U.S. Occupational Safety and Health Administration's Voluntary Protection Programs framework recommends quarterly audit cadence for dock-safety controls.
In March 2026 Cojo's lead estimator (NICET Level III, OSHA-30 certified) walked trailer chock placement procedure with the safety committee at a Hillsboro distribution warehouse. The site received 24 heavy-duty rubber chocks the same week, sized for the Class 8 trailer fleet that loads at 12 dock positions. The walk identified one tandem-axle placement error (chocks at the forward axle instead of rearmost) that had developed in the months since the last OSHA audit. Correction was procedural -- updated dock-operator training and a posted reference diagram at each dock door.
Trailer chock placement combines OSHA pair-of-chocks rule, rearmost-axle priority, slope-direction adjustment, and chock-size selection. Cojo's site walks cover the full placement sequence as part of broader parking-products and dock-safety planning. Get a custom quote.
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