noun
nail sticking through; protruding nail
Refers to a nail that has been driven through a board and its point is sticking out the other side. A technical term in woodworking and carpentry.
裏釘が出ているので、金槌で叩いて曲げてください。
The nail is sticking through, so please hammer it down and bend it.
この板の裏側には裏釘が何本も見える。
On the back side of this board, you can see several protruding nails.