We'd call them "boltcutters" - not "a boltcutters" or "some boltcutters", just "boltcutters" (like trousers (although I am led to believe (by the Guardian's fashion chappies, who may well be winding me up) that in certain very on-trend circles, it is correct to refer to "a trouser", as in "he cuts a very fine trouser")).

If you were asking where they were, you'd say "Where are the boltcutters?"