A peg or nail driven into a wall or post for hanging things; a rare term, more commonly expressed as 掛け釘(かけくぎ) or simply 釘(くぎ) with context.
I drove a peg into the wall and hung my hat on it.
Compound of 掛け (kake, 'hanging') + 釘 (kugi, 'nail'). The exact historical derivation is uncertain, but the word transparently means 'hanging nail'.