A sheath. Usually swords go into it, but I guess knives could too.
A sheathe protects users and curious children from being cut.
A knife block.
the bed
belt loop...?
Yes, knives is a noun, a plural, common, concrete noun. A noun is a person place or thing and knives are a thing.
Always called it a tree stand.
A cutler
The "necklace" piece is called a Lanyard. Then the other piece that holds the card is called an ID Protector.
Butter knives.
blademaniac
A cutler
knife maker or forger
Pony Tail Holder. At least that is what I call it. Lol. Ponio Kirby grip Alice band
The thing that is a sash like object that holds a katana is called an obi.