Buy OSRS Mith grapple
The mith grapple is an Old School RuneScape item that goes in your ammunition slot. You use it with a crossbow to cross special Agility shortcuts. Both the grapple and the crossbow must be equipped. It does not work with the love crossbow, light ballista, or heavy ballista.
Many achievement diary tasks ask you to use these grapple shortcuts. Most shortcuts need certain Agility, Ranged, and Strength levels. The Armadyl area of the God Wars Dungeon is the one exception, since it only needs 70 Ranged.
Each time you use the grapple, there is a 1 in 25 chance it breaks. It will never break in the Hallowed Sepulchre or on the Shayzien Agility Course.
You can make a mith grapple yourself. Smelt a mith grapple tip from a mithril bar with 59 Smithing. Attach the tip to a mithril bolt with 59 Fletching, then add a rope. The item is tradeable at every stage, so buying one saves you the skill grind and the crafting time. It is a members only item, and it weighs almost nothing, so it is easy to carry anywhere you need to grapple.