Be careful! That knife is sharp! Don’t prick yourself with that pin! Working with sharp things means taking special care. But some things have to be sharp to work well. A dull knife or a pin without a point isn’t much help at all.
Sharp things have a special shape that makes work easier. They are really all one kind of machine – a machine called a wedge. The thin, sharp end of a wedge can cut or push into things easily. Then the thicker part of the wedge can push through. Knives, saws, and scissors are wedges for cutting. Pins, nails, and needles are wedges used for pushing into or through things. The point makes it easy for the drawing pin to stick into a notice board, for the nail to push into wood, and for the needle to push through cloth.
Axes and metal wedges are used to push the sharp edge into a log. Then the wider part spreads the wood and makes it split.
Many boats have a wedge-shaped bow, or front end. The bow cuts through the water and makes it easy for the boat to glide along.
Picture Credit : Google