die Zacke
prong / point
A pointed, protruding edge or tip on an object, such as on a fork, a saw, or a crown.
Eine Zacke ist aus der Gabel herausgebrochen.
A prong has broken off the fork.

prong / point
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prong / point
A pointed, protruding edge or tip on an object, such as on a fork, a saw, or a crown.
Eine Zacke ist aus der Gabel herausgebrochen.
A prong has broken off the fork.

The adjective 'zackig' is derived from 'Zacke' (prong / point). 'Zackig' can mean 'having points or prongs', but also colloquially 'quick' or 'brisk'. This second meaning is closely connected to the idiom 'einen Zacken zulegen' (to pick up the pace).
Die Bergkette hat ein sehr zackiges Profil am Horizont.
The mountain range has a very jagged profile on the horizon.
A 'Zacke' (prong / point) is usually part of a larger object. Typical formulations are therefore 'die Zacken einer Gabel' (the prongs of a fork), 'die Zacken einer Säge' (the teeth of a saw), or 'die Zacken einer Krone' (the points of a crown).
Vorsicht, die Säge hat sehr scharfe Zacken.
Careful, the saw has very sharp teeth.
The colloquial idiom 'einen Zacken zulegen' means 'to speed up' or 'to hurry up'. The verb 'zulegen' is separable here; the prefix 'zu' goes at the end of the sentence.
Leg mal einen Zacken zu, wir kommen sonst zu spät!
Pick up the pace, or we'll be late!
The request 'einen Zacken zulegen' is clearly colloquial. You use it among friends or in informal situations, but not in formal writing.
Leute, wir müssen einen Zacken zulegen, die Deadline ist morgen!
People, we need to pick up the pace—the deadline is tomorrow!
tip / top / lace
'die Spitze' and 'die Zacke' can both mean something pointed on an object. 'die Spitze' usually means the single narrow end of something, for example a pencil or a knife. 'die Zacke' is more like a pointed projection or tooth, often one of several, such as on a saw, a fork, or a crown. The words can be confused because a 'Zacke' is also a kind of point. But not every 'Spitze' is a 'Zacke': a 'Zacke' sticks out clearly and often belongs to a row.

An der alten Säge fehlt eine Zacke, deshalb schneidet sie nicht mehr sauber.
An old saw is missing a tooth, so it no longer cuts cleanly.
In der Küche prüft das Kind vorsichtig die Spitze des Messers.
In the kitchen, the child carefully examined the tip of the knife.