Grappling hooks pull you toward blocks and let you swing and scale terrain. Better hooks reach farther, latch onto several points at once, or reel faster — a mobility essential from the first cave to the final boss arena.
The Static Hook (from the Martian Saucer) is a favourite for building since it holds you on the line, while the Lunar and Anti-Gravity Hooks give the best reach and control for combat.
Craft the basic Grappling Hook from a Hook (a Skeleton drop) plus three chains. Many others — gem hooks, Bat, Slime and Amber hooks — come from crafting, chests and enemies.