Born in or around the year 1618, few details on the life of instrument maker Walter Hayes are known for certain, although he is referenced in an entry of the Diary of Samuel Pepys. On 16 September 1664, Pepys described him as the ‘mathematical instrument maker at Moorefields’. His shop there was known as the 'Cross Daggers, next door to the Pope's Head Tavern near Benthlem Gate in Moorfield' but he also had another workshop situated in Cornhill, also in London. Hayes used the depiction of crossed daggers as his shop sign and in the printed advertisements he made from the 1650s.
Primarily a maker of mathematical instruments made from silver, brass and wood, Hayes was a skilled engraver and took many apprentices during his three decades of instrument making including Edmund Culpeper. There is evidence that Hayes also operated as a book-seller on behalf of others, and some of the books that he sold may have accompanied, or were linked to, the mathematical implements that he sold.
A member of the Grocer's Guild, Hayes' instruments included quadrants, astrolabes, protractors and other measuring tools. In addition to engraving his name on objects, in some cases he engraved a stylised monogram to indicate he was the maker and this may have been a form of early modern branding. He is thought to have died in either 1695 or 1696.