The mainmast was in danger of falling down, until the backstay broke and saved it.
From the heraldtribune.com
The mast of a ship is held in an upright position because of the forestay and the backstay.
From the abcnews.go.com
Their use allows the leeward backstay to be completely slackened so that the boom can be let fully out.
From the en.wikipedia.org
The running backstay snapped which forced the pair to retire and left them with repairs to carry out overnight.
From the telegraph.co.uk
May be used to attach the backstay or mizzen sheets.
From the en.wikipedia.org
American team Quantum leads by just seven points after problems with the backstay at the last event in Cagliari left them well down the rankings in fifth place.
From the telegraph.co.uk
For strength and support, a rod called the backstay may extend from either end of the rear axle to the reach, the pole or rod joining the hind axle to the forward bolster above the front axle.
From the en.wikipedia.org
More examples
A stay that supports the back of something
On a sailing vessel, a backstay is the piece of standing rigging that runs from the mast to the transom of the boat, counteracting the forestay and jib. The backstay is an important sail trim control and has a direct effect on the shape of the mainsail and the headsail.
(BACKSTAYS) Stays running from a masthead to the vessel's side, slanting a little aft. (See STAYS.)
(Backstays) The stays that support the topmast with a beam or stern wind. The topmast shrouds or rigging. (See "Shifting Backstay" and "Preventer.")
A support for the mast to keep it from falling forward.
A stay (line or cable) used to support the mast. The backstay runs from the masthead to the stern and helps keep the mast from falling forward.
A short strip of leather that connects the quarters down the back of the shoe.
Mast support leading aft, part of the standing rigging
Provides rearward support to a mast. A RUNNING BACKSTAY can be triced out of the way when not in use.