A Bridport dagger (q.v.). St. Johnstone's tippet.
or rather Halster. A rope for the neck or halse, as a horse's halter. (Anglo-Saxon, hals, the neck; but there is also the word hælfter, a halter.)
A thievisher knave is not on live, more filching, no more false; Many a truer man than he has hanged up by the halse [neck].
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894
More on Halter from Infoplease: