Why jeans have a tiny pocket. Why pen caps have a hole. Short, sourced answers to the questions everyday objects raise, each with a one-minute video.
Office
Most pencils are hexagonal because the flat sides stop them rolling off a desk and give your fingers something to grip. Faber-Castell says the shape replaced round pencils for exactly that reason. The hexagon also suits the factory: pencils are cut from glued wooden slats, and six-sided pencils can fit more per slat than round ones.
Kitchen
Crackers have holes, called docking holes, so they bake flat and crisp. Before baking, pins press into the thin dough, pinning its layers together and giving steam a way out. Without them, steam trapped between the layers would inflate the cracker into a hollow, uneven pillow. Bakers prick pie crusts with a fork for the same reason.
Money
The ridges, called reeding, began as an anti-theft feature. When coins were made of gold and silver, people clipped or filed metal from the edges and still spent the coins at full value. A ridged edge made any trimming obvious. Everyday coins no longer contain precious metal, but the ridges stayed, and they help people tell coins apart by touch.
Home
The tiny hole at the bottom of a padlock is a drain. Rain gets in around the shackle and through the keyhole, and the hole lets that water, and grit with it, run out instead of pooling inside, where it can rust the parts or freeze and jam the lock. It is not a keyhole and opens nothing.
Home
The small square at the sealed end of a toothpaste tube is an eye mark, a printed target for a light sensor on the production line. The filling machine uses it to line the tube up before sealing and trimming it. It says nothing about the ingredients. Its color just needs to stand out from the background.
Cars
The small arrow or triangle beside the fuel pump icon points to the side of the car where the fuel door is. If it points left, the filler is on the left; if it points right, it is on the right. Ignore which side the pump's hose is drawn on: only the arrow is meant to show the side.
Travel
The tiny hole is a breather or vent hole in the middle pane of a cabin window. It lets cabin air into the gap behind that pane, so the outer pane carries the pressure difference while the middle pane stays unloaded as a backup, ready if the outer one fails. The pane you can touch is only a scratch guard.
Cars
The black dots are the edge of the frit, a black ceramic enamel fused onto the windshield when it is heated and bent. The solid band hides the polyurethane glue holding the glass in and shields it from UV light. The shrinking dots soften the jump from black to clear, so the hotter band doesn't distort the glass.
Office
The hole in a pen cap is a safety feature. If a cap is inhaled and lodges in the airway, the hole lets some air through so the person can keep breathing until doctors remove it. The ISO 11540 safety standard covers caps on pens likely to be used by children up to age 14.
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