Bags of salt can be purchased from any Slayer Master, and are used to finish off rockslugs that are at 240 life points or less. When used, the rockslug disintegrates, drying up and shrinking, consuming the bag of salt. Using a bag of salt on a rockslug with 241 or more life points has no effect, and still consumes a bag of salt. Bags of salt are also used during the Fur 'n' Seek quest in order to salt the hides of various animals. Bags of salt are also a required item in the Icthlarin's Little Helper quest, as players are required to have a bag of salt in order to access "Flashback 3".
The effect of salt on rockslugs in RuneScape mirrors the effects of salt on slugs on Earth. The salt provokes an osmotic reaction in which the slug's internal liquids are drawn out to dilute the salt and thus maintain the slug's external mucus layer.