The Rope/Vine Arrow:

The rope arrow will quickly become a Keeper's most valuable asset. The rope arrow is a reinforced steel arrowhead on a shaft wrapped in rope. Upon impact, the rope uncoils and falls downward from the arrow shaft, thus allowing one to reach areas otherwise unaccessible. The arrow's steel head can penetrate all earthy materials save stone or rock. This includes wood and moss.

Vine arrows work in the same way as rope arrows but can also cling to grating as they latch into place using many small vines.