Forklift specification sheets are written in a vocabulary that assumes you already know it, and most buyers nod through terms that are quietly deciding whether the truck will fit their building. Load centre, free lift, right angle stack, backrest height, triplex, derate: each of these is a number that can make a machine unsuitable, and each is routinely skipped in a sales conversation. This glossary covers the terms that actually change a purchase decision, grouped by what they describe, in plain language and with the reason each one matters.
Get Free Quotes 👑Rated capacity is the maximum weight a truck can lift, but it is only meaningful alongside load centre, which is the horizontal distance from the fork face to the centre of gravity of the load. The American standard is 24 inches, and every rated capacity assumes it. A load whose weight sits farther out than 24 inches, a long crate or a deep pallet, effectively weighs more as far as the truck is concerned. This is why a 5,000 lb truck can be unable to lift a 4,000 lb load: the weight is fine and the load centre is not.
Derate means the reduction in rated capacity caused by lift height, attachments, or a load centre beyond standard. A nominal 5,000 lb truck may be rated considerably lower at full mast extension or with a fork positioner fitted. The capacity data plate on the truck is the legal statement of what it can lift in its current configuration, and under OSHA 1910.178(a)(5) it must be changed to agree with any modification the manufacturer has approved. The plate, not the brochure, is the number that governs.
Free lift is how far the forks rise before the mast itself starts extending upward. On a simple two-stage mast it is close to zero, so the mast grows the moment the forks leave the floor. Inside a trailer or a shipping container that is a problem, because the mast hits the roof before the forks are high enough to stack. Full free lift, which generally requires a three-stage mast, raises the forks most of the way up the inner section before anything moves. If any work happens inside a container, this is a requirement rather than an option.
A duplex or two-stage mast has one moving section: cheapest, best visibility, minimal free lift. A triplex or three-stage adds a section, giving more height and real free lift within the same collapsed dimension, at the cost of more steel in the operator sightline. A quad mast adds a fourth for extreme heights and is rare. The rule is to buy the fewest stages that reach your top beam with the free lift you need, because every extra section costs visibility, capacity and money.
Lowered height, also called collapsed or mast lowered height, is how tall the truck stands with the forks on the floor. Extended height is the top of the mast at full lift. Lowered height decides whether the truck fits through your door, into a trailer or into a container, and it is frequently the specification that disqualifies a machine nobody thought to check. A standard shipping container has roughly 94 inches of interior height and a high cube about 106 inches.
The load backrest is the vertical guard behind the forks that stops a load tipping back toward the operator. Its height matters because a tall, unstable load needs a tall backrest to be carried safely, and standard backrests are often shorter than buyers assume. If you handle tall stacked loads, specify the backrest height rather than accepting the default, and note that a taller backrest can add to the truck lowered height and therefore affect door clearance.
Right angle stack aisle, usually written RAS, is the clear distance between rack faces that a truck needs to turn ninety degrees and place a pallet square into racking. It combines turning radius, truck length to the fork face, load length and working clearance. Published figures assume a 48 by 40 inch pallet on 42 inch forks, so your real requirement is larger if your pallets are longer or carried the long way, and you should add six to twelve inches of working clearance on top in any case.
Outside turning radius is the circle swept by the outermost point of the truck. It is related to but not the same as right angle stack, which is the number that actually matters for racking. Wheelbase, the distance between front and rear axles, drives both: a shorter wheelbase turns tighter and rides harsher. These three numbers together describe how the machine behaves in an aisle, and the one to compare across quotes is right angle stack with your pallet size.
Cushion tires are solid rubber on a steel band, short and tight-turning, for smooth indoor concrete only. Pneumatic tires are air-filled with real tread, for rough ground, with the best ride and the possibility of punctures. Solid pneumatic is solid rubber in a pneumatic profile: the ground clearance and tread without the punctures, and the right default for mixed duty. Polyurethane is for electric warehouse equipment on clean smooth floors. Non-marking versions exist for finished floors and are required in food, pharmaceutical and cleanroom environments.
Hour meter is the running-time counter and the headline number, though it needs corroborating. Serial number identifies the specific machine and lets you verify its build independently. Side shift means the carriage moves left and right. Fork positioner means the forks move in and out hydraulically. Third and fourth function refer to the spare hydraulic circuits those attachments need. As-is means no representation and no recourse. Off-lease usually means a fleet truck maintained on schedule and retired on a calendar, which is generally a good sign.
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The horizontal distance from the fork face to the centre of gravity of the load, standardised at 24 inches in the United States. Every rated capacity assumes it. A load whose weight sits farther out effectively weighs more to the truck, which is why a 5,000 lb machine can fail to lift 4,000 lb.
How far the forks rise before the mast begins extending upward. Near zero on a two-stage mast, substantial on a three-stage. It matters inside trailers and containers, where a mast that grows immediately hits the roof before the forks are high enough to stack.
A duplex or two-stage mast has one moving section: cheapest, best visibility, minimal free lift. A triplex adds a section for more height and real free lift within the same collapsed dimension, at the cost of visibility and capacity. Buy the fewest stages that reach your top beam.
The clear distance between rack faces a truck needs to turn ninety degrees and place a pallet square into racking. Published figures assume a 48 by 40 inch pallet on 42 inch forks, so add for longer pallets and add six to twelve inches of working clearance.
The reduction in rated capacity caused by lift height, attachments, or a load centre beyond standard. The capacity data plate states what the truck can lift as currently configured, and OSHA requires it be changed to match any approved modification. The plate governs, not the brochure.
How tall the truck stands with the forks on the floor. It decides whether the machine fits through your door, into a trailer or into a container, and it is the specification most often overlooked. A standard container has about 94 inches of interior height, a high cube about 106.