der Barren
bar / ingot
A block-shaped piece of cast metal, especially precious metal such as gold or silver.
Die Bank lagert Goldbarren in ihrem Tresor.
The bank stores gold bars in its vault.

bar / ingot
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bar / ingot
A block-shaped piece of cast metal, especially precious metal such as gold or silver.
Die Bank lagert Goldbarren in ihrem Tresor.
The bank stores gold bars in its vault.

You can easily recognize the meaning of 'Barren' from the context. If it is about money, metals such as gold or silver, or a vault, it means a metal block. If it is about sports, gymnastics, or a gymnasium, it means the sports apparatus.
Der Dieb stahl einen schweren Goldbarren aus dem Museum.
The thief stole a heavy gold bar from the museum.
In the meaning of 'Metallstück' (piece of metal), 'Barren' is often used as the second part of a compound that names the metal. The most common examples are 'Goldbarren' (gold bar) and 'Silberbarren' (silver bar).
Viele Anleger investieren in Goldbarren, um ihr Vermögen zu sichern.
Many investors invest in gold bars to protect their wealth.
When the gymnastics apparatus is meant, it is almost always used with the preposition 'an' in the dative. So a typical phrasing is 'am Barren turnen' (to do gymnastics on the parallel bars) or 'eine Übung am Barren machen' (to do a routine on the parallel bars).
Er hat seine Übung am Barren fehlerfrei absolviert.
He completed his routine on the parallel bars without any mistakes.
block / pad
'der Block' and 'der Barren' can both mean a solid, heavy piece of material. 'Block' is more general: a block can be made of stone, wood, ice, or another firm material. 'Barren' is used especially for cast metal, particularly for gold or silver. Learners may confuse the words because an ingot often looks like a small block. If the material is important and you are talking about metal or precious metal, 'Barren' is more precise. For other massive pieces, 'Block' is more natural.

Die Bank bewahrt die Goldbarren in einem sicheren Raum auf.
The bank keeps the gold bars in a secure room.
Vor der Werkstatt liegt ein schwerer Block aus Stein.
In front of the workshop, there is a heavy block of stone.