HandleThe handle, which the operator holds to push and steer from behind.
Blade control barMust be held against the handle for the blade to run. Letting go stops the blade within 3 seconds. Also called the bail.
Grass catcherThe grass catcher, or bag, which collects the clippings.
EngineThe engine, on top of the deck. On most rotary mowers the blade is fixed straight to its crankshaft.
DeckThe steel shell over the blade that holds the engine and wheels. Also called the cutter housing.
BladeOne long bar that spins flat under the deck, about the middle.
From the side: 11 6
Starter ropePulled by its grip to start the engine by hand. Also called the pull cord.
Fuel capThe fuel cap, closing the petrol tank on top of the engine.
Air filterThe air filter, which cleans the air going into the engine.
Spark plugThe spark plug, which lights the fuel. Its wire is pulled off before anyone reaches under the deck.
WheelsThe wheels, one at each corner of the deck.
Height adjusterA lever that raises or lowers the deck. It sets how short the grass is cut.
How this list was compiled: Read 2026-09-27. (1) Wikipedia, Lawn mower, https://en.wikipedia.org/wiki/Lawn_mower : a rotary mower’s blade spins about a vertical axis; its main parts are the cutter deck housing, which houses the blade, and the blade drive, the blade usually mounted directly on the engine crankshaft; engines usually need a manual pull crank to start; the deck is typically steel; some have a grass catcher to bag the clippings; many have a dead man’s switch that stops the blade when the handle is let go. (2) 16 CFR part 1205, Safety Standard for Walk-Behind Power Lawn Mowers, via Cornell LII, https://www.law.cornell.edu/cfr/text/16/1205.3 and https://www.law.cornell.edu/cfr/text/16/1205.5 : blade, engine, handle, manual starting (the cord mechanism), the blade housing as a shield; a blade control that must be held for the blade to run and that stops it within 3.0 seconds of release. (3) Maker’s manuals on archive.org (Weed Eater WE261, https://archive.org/details/manualsbase-id-204263 ; Briggs & Stratton 2400 XL, https://archive.org/details/manualsbase-id-194338 ): height adjustment lever, recoil starting, oil fill cap and dipstick, air filter, spark plug and its wire, fuel cap, grass catcher, discharge chute. Licence: own work
The drawing: Drawn for this site by script, 2026-09-27. Own work, nothing traced. Licence: own work
How it works
These are the labeled parts of a lawn mower on a walk-behind petrol rotary mower: first side-on, then the deck from underneath to show the blade. Start with the 7 main parts.
Read the full guide
Driving it
The operator pushes from behind by the handle. The blade only runs while the blade control bar is held against the handle; let go and it stops. The starter rope, pulled by its grip, starts the engine.
The cutting parts
The engine sits on the deck, a steel housing on four wheels. Underneath, one blade spins flat about the middle, usually fixed straight to the engine's shaft. The height adjuster sets the cut, and the grass catcher collects clippings.
Before anyone reaches under the deck, stop the engine and pull the wire off the spark plug so it cannot start.
Questions and answers
What is the bar on a lawn mower handle called?
The blade control bar, also called the bail or dead man's control. The blade runs only while it is held; US safety rules require the blade to stop within 3 seconds of letting go.
What is the deck on a lawn mower?
The steel housing that covers the blade. The engine sits on top of it and the wheels are fixed to it.
How does a rotary mower cut grass?
A single blade spins very fast in a flat circle under the deck, cutting the grass like a scythe. On most mowers the blade is bolted straight to the engine's shaft.