Thieving

Pickpocket NPCs found in the Town for coins and loot. Higher-level NPCs require a higher Thieving level but yield more XP and better rewards per steal.

Lockpicks

Equip a lockpick to raise your pickpocket success chance. Its efficiency multiplies the bonus you gain for every Thieving level above the NPC's requirement. Higher-tier lockpicks require a higher Thieving level.

A failed pickpocket stuns you: that attempt yields nothing, and the following frame is skipped entirely with no XP or loot. Raising your success chance therefore matters more than the raw per-steal reward suggests.

Lockpick tier efficiency multiplier

Depending on the difference in tier between the lockpick used for pickpocketing, and the level required for pickpocketing npcs, you can receive an additional mult to your standard tool efficiency. The effect of this is that when you're pickpocketing lower tier npcs your tool has a much higher efficiency with all the bonuses that entails.

For normal tools, their tier is determined by their minimum level required to equip. For the Heirloom Lockpick, its tier is defined by your current thieving level. The heirloom's tool efficiency itself is calculated separately as described in Heirlooms.

For npcs, the tier depends on the minimum required level for pickpocketing the relevant npcs.

The level ranges for each tier are shown below:

The exact multiplier you get applied to your tool efficiency depends on the tier difference as calculated using the formula: $Tier\ difference = tool\ tier - npcs\ tier$. The tool efficiency is multiplied as per the table below (— indicates no mult applied)