Ferrule and Rings

Ferrule noun - A metal cap or band placed on a wooden pole to prevent splitting.

Rings and ferrule are semantically related. In some cases you can replace term "Rings" with "Ferrule", this nouns are similar.

Rings noun - Gymnastic apparatus consisting of a pair of heavy metal circles (usually covered with leather) suspended by ropes; used for gymnastic exercises.

Ferrule and rings are semantically related. Sometimes you can use "Ferrule" instead a noun "Rings".