Buy RS3 Sinew
Sinew is a Cooking item in RuneScape 3. Players make it by using raw beef, raw wolf meat, raw bear meat, raw yak meat, or raw ugthanki meat on a range. It only needs level 1 Cooking and gives 3 Cooking experience. It cannot be made on a fire, since the meat will just cook instead.
The main use for sinew is making crossbow string. With level 10 Crafting, players can spin sinew on a spinning wheel to get crossbow string and 15 Crafting experience. Sinew is not the same as flax, so it does not work for regular bows.
Sinew also matters at high levels. With level 110 Crafting, players can combine 2 sinew with 10 thread and 2 apex sinew to make 10 masterwork sinew. Masterwork sinew is a key material for masterwork ranged armour, which needs 1200 in total for a full set.
Players also need 15 sinew to string Dalia's lute before she lets them use her tree nursery in Wendlewick. Sinew is tradeable, noteable, and free to play. It weighs almost nothing, so it is easy to carry in bulk for training or crafting goals.