The jointer: the machine that erases
A saw blade cuts a line. A jointer's cutterhead removes material in scoops, thousands per minute — which is why jointer accidents are rarer than table saw accidents but so much worse per incident. What a cutterhead touches, it doesn't cut; it erases.
Machines and tools vary by brand, model, and age. Your manual outranks this page — read it first.
The machine's job explains its danger. A jointer flattens a face or straightens an edge by carrying wood over an open spinning cutterhead set into the table — the cut happens on the underside, exactly where you can't see it, directly beneath your pushing hands. Every jointer rule is about one thing: your hands crossing that head with nothing between them and it.
Push blocks, always
Face jointing — board flat on the table, palms on top — is the position where a slip, a knot letting go, or a board splitting drops your hand straight onto the head. Rubber- soled push blocks change the geometry completely: the block absorbs the drop, and your hand rides three inches above the action. Use two blocks, one per hand, walking them hand-over-hand down the board as it feeds.
Edge jointing keeps fingers on the board's face and the fence side, never hooked over the top edge where they'd trail into the cutterhead's path — and never wrapped under the outfeed end.
The minimum-length rule
Most manuals set the shortest safe workpiece around 12″, and the reason is leverage: a short board can drop into the cutterhead opening between the tables, and when the head catches it, the board leaves — sometimes in pieces — with your hands following through the space it occupied. Joint long, then crosscut to length; the few extra inches of wood are a good trade.
The guard is never in your way
The spring-loaded "pork chop" guard swings closed over every inch of cutterhead the board isn't currently using. It feels like a nuisance for about a week; after that it's invisible — right up until the day a push block slips and it's the only thing between knuckles and knives. If yours doesn't snap shut on its own, fix the spring before the next board, and if a rabbeting cut wants the guard off, remember that manuals stopped recommending rabbeting on jointers a generation ago. A router does it better with everything covered.
The jointer's whole discipline is three things: push blocks between hands and cutterhead, boards long enough to bridge the tables, and a guard with a working spring. With those three in place, the machine with the worst injury reputation in the shop runs, day to day, as one of the most predictable.