RUST Sewing Kits fall into the component category of items. These components are used in the creation of multi-tiered items, as well as recycle fodder for players to obtain game building and crafting resources as well as Scrap.
Sewing kits are lootable from an assortment of low-to-mid-tier crates and barrels, as well as being dropped by some scientist types with an emphasis put on Tunnel and Underwater Dwellers.
Aside from the Bed, sewing kits are exclusively used to craft a variety of armor pieces ranging from mid to the highest tier in quality. Most notably, they are used in the creation of Metal Chestplates and Metal Facemasks.
With regards to their recycle yield, sewing kits are a provider of both rope and cloth. It is common practice in RUST to purchase Tactical Gloves from the Outpost monument at any point in the game to more easily acquire large amounts of sewing kits, either for them at face value or to be recycled to make the aforementioned armor.
It is a good idea to keep a large amount of these on-hand throughout wipe progression, but especially after the acquisition of higher workbenches.