der Zaun
fence
A structure made of wood, metal, or wire that marks off a property or an area.
Die Nachbarn haben einen neuen Zaun um ihren Garten gezogen.
The neighbors have put up a new fence around their garden.

fence
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fence
A structure made of wood, metal, or wire that marks off a property or an area.
Die Nachbarn haben einen neuen Zaun um ihren Garten gezogen.
The neighbors have put up a new fence around their garden.

Verbs that describe creating or putting something up are often used with 'Zaun' (fence). Typical phrases are 'einen Zaun bauen' (to build a fence), 'einen Zaun errichten' (to erect a fence), or, more colloquially, 'einen Zaun ziehen' (to put up a fence).
Wir müssen um den Garten einen neuen Zaun bauen.
We need to build a new fence around the garden.
Pay attention to the case after prepositions. Movement is expressed with the accusative, while position is expressed with the dative.
Der Ball flog über den Zaun.
The ball flew over the fence.
The idiom 'mit dem Zaunpfahl winken' (to wave with the fence post / to drop a huge hint) uses a part of the fence, the 'Zaunpfahl' (fence post). The image of such a large object as a 'Wink' (hint) makes it clear that the hint is extremely obvious.
Sie hat mit dem Zaunpfahl gewinkt, indem sie ständig auf ihre Uhr schaute.
She dropped a huge hint by constantly looking at her watch.
wall
'die Mauer' and 'der Zaun' both mark off an area, for example a property or a garden. A 'Mauer' is solid, massive, and usually made of stone, brick, or concrete. A 'Zaun' is built more lightly, for example from wood, metal, or wire, and you can often see through it. The words can be confused because both can stand along property boundaries. If the boundary seems heavy and closed, you say 'Mauer'. If it consists of posts, boards, or wire, 'Zaun' is more natural.

Tim repariert heute den Zaun vor dem Haus.
Tim is repairing the fence in front of the house today.
Die Kinder spielen Fußball neben der alten Mauer.
The children are playing soccer next to the old wall.