A stay is a piece of rigging equipment that is used to support the entire weight of a mast on its top side. It’s a long, thick rope that runs down from the upper end of every mast to the lower end of the boat. The stays run down in a perpendicular direction and support on either side of a mast’s stem. Masts are generally built with a center mast and these remain relatively static while the sails are held up by the stays. There are some mooring stays that are designed so the mast can be secured in a normal position relative to the clew arrangement while the main sail is left free and the stays act as a rudder.
In order keeping your boat upright you will need a way to raise the mast so that the stays are able to act as rudders and in order to allow the windlass to pass through. This can be achieved using a boom or a rigger. In a nautical sense a boom is basically a piece of equipment that raises a mast either frontward or backwards depending upon the situation. A rigger is a lifting device that allows for the raising of a mast without the use of a boom.
Now that you understand the basics you should know that in order for a stay to perform at its best you must have two separate pieces which are: a mast guard and a leech. The mast guard is designed to protect the lower rigging while the leech attaches to the top of the mast in order to prevent windlass passage through. If you want to be really safe you may install both the guard and the leech together. The stay is what actually lifts the mast and it’s a simple spring-based mechanism that raises and lowers the mast with the assistance of the boom. To complete the look, you’ll want to add some wire ropes to help move the leech from place to place and to give it a more finished look.