thumbtack

(t̸humtak′)

noun

a tack with a wide, flat head that can be pressed into a board, etc. with the thumb

See thumbtack in American Heritage Dictionary 4

noun
A tack with a smooth, rounded head that can be pressed into place with the thumb.
transitive verb thumb·tacked, thumb·tack·ing, thumb·tacks
To affix with a thumbtack.
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