Knock box

Takes the spent puck off the basket and holds the day's grounds until they are emptied, without the impact travelling into the portafilter or the wrist.

A container with a bar across it, and the bar is the entire design. The puck is knocked against that bar, and how the bar behaves decides everything: a compliant sleeve over a rigid core absorbs the impact and lets a light knock release the puck, while a hard, thin or badly supported bar sends the shock straight back through the portafilter's lugs and into the barista's wrist and elbow, hundreds of times a day. Bar HEIGHT is the second variable and it is set by the same reasoning — a bar too low forces the arm to swing further and hit harder, and a bar too high catches the spouts instead of the rim. Everything else is containment: grounds are wet, acidic and heavy, they compact under their own weight, and they ferment. A box with no liner, no drainer and no defined emptying point becomes a sour smell at the busiest station on the bar, and the smell is noticed by guests long before it is noticed by the team standing in it.

• Size the box to how often it will actually be emptied, not to the day's volume, and then write the emptying into the shift rather than leaving it to whoever notices. A box sized for a whole day is a box that will be lifted full, which is heavy, and it is a box that will be fermenting by mid-afternoon in a warm venue.
• Judge the knock bar by compliance and by height, and test it with a real portafilter before you commit. Knock a puck out and feel where the shock goes: if it comes back up the handle, that box will be paid for in wrists over a year. This is the only test that matters and it takes one shot to perform.
• Place it within the tamping reach, on the same side as the working hand, so the spent puck never crosses the lane. A knock box on the wrong side of the barista means a loaded portafilter travelling across the bar twice per drink, past everything clean.
• Insist on a removable liner or an inner bin. The container that touches wet grounds should be the one that leaves and gets washed, not the one bolted to the counter, and a box that has to be carried to the sink whole is a box that gets emptied less often than it should.
• Check the emptying route before you buy the capacity. Wet grounds are dense and a large box full of them is a two-handed lift through a busy bar to a bin that may be outside — and that route, not the box, is what actually decides how often it happens.
• Look for standing liquid in the design. Grounds hold water, water collects at the bottom, and a box with no drainer and no drain-off is a box whose contents are wetter, heavier and more sour every hour. A raised false floor is worth more than any other feature on the list.
• If an in-counter chute is being considered, decide it with the joinery and specify how it closes and how it is cleaned. An open hole beside a milk station is a hygiene question, and answering it after the counter is built means answering it badly.