camshaft

"After I finished reading the book, I replaced it on the shelf. "

"My sister is very helpful, especially when it comes to organizing things. "

"It fits the purpose."

"The mechanic fixed the broken bicycle chain. "

"The car's engine used a piston to compress the air and create power. "

"The ancient Romans used a powerful siege engine to break down the city walls. "

"The plumber replaced the leaky valves under the sink to stop the water from dripping. "

"By now, you must surely know which is which."

"The waiter carried the trays of food smoothly, avoiding any spills. "

"The archer carefully examined the shaft of the arrow before shooting. "

"to allow a servant his liberty;  to allow a free passage;  to allow one day for rest"

"The smell of coffee activates my brain in the morning. "