Stays are the heavy ropes, wires, or rods on sailing vessels that run from the masts to the hull, usually fore-and-aft along the centerline of the vessel. The stay that runs aft is called backstay and the stay that runs forward is called forestay or just stay.
Lines running from the mast to the side of the boat are usually called shrouds instead.
To "miss stays" is an unsuccessful attempt to tack.
Types of stays
"Stay. A large strong rope extending from the upper end of each mast towards the stem of the ship, as the shrouds are extended on each side. The object of both is to prevent the masts from springing, when the ship is pitching deep. Thus stays are fore and aft. Those led down to the vessel's side are back-stays. The fore-stay reaches from the foremast-head towards the bowsprit end. The main-stay extends to the ship's stem. The mizzen-stay stretches to a collar on the main-mast, immediately above the quarter-deck. The fore-topmast stay goes to the end of the bowsprit, a little beyond the fore-stay, on which the fore-topmast staysail runs on hanks. The main-topmast stay attaches to the hounds of the foremast, or comes on deck. The mizzen-topmast stay goes to the hounds of the main-mast. The top-gallant, royal, or any other masts, have each a stay, named after their respective masts. Spring-stay is a kind of substitute nearly parallel to the principal stay, and intended to help the principal stay to support its mast. On a steamer, an iron bar between the two knees secures the paddle-beams. (See funnel stays).
"To stay. To tack, to bring the ship's head up to the wind for going about; hence to miss stays, is to fail in the attempt to go about. In stays, or hove in stays, is the situation of a vessel when she is staying, or in the act of going about. A vessel in bad trim, or lubberly handled, is sure to be slack in stays, and refuses stays, when she has to wear."
- Smyth, William Henry; Belcher, Edward (1867). The sailor's word-book: An alphabetical digest of nautical terms, including some more especially military and scientific ... as well as archaisms of early voyagers, etc.. London: Blackie and Son. pp. 652-653. http://books.google.com/books?id=y7HqO9XAwk8C&dq=sailor%20beached%20-beaches&lr&as_drrb_is=q&as_minm_is=0&as_miny_is&as_maxm_is=0&as_maxy_is&num=100&as_brr=4&pg=PA653#v=onepage&q&f=false.