Wall safe

Wall safes are found in the Rogue's Den, where four of them can be cracked providing you have a Thieving level of 25. Successfully cracking a safe yields 70 thieving experience. If the player fails to crack a safe, a floor trap will spring and deal 20-60 life points damage. Bringing a healing familiar such as a Bunyip is recommended, but not mandatory, since there is a bank just seconds away. A stethoscope increases the success rate of cracking the safe. These can be purchased from Martin Thwait once you reach 50 thieving, who can be found wandering around the general Rogue's Den area.

After receiving damage (between 20-70 points), players can right-click the floor allowing 2 options: Examine which says "it's the floor"; and Search, which does not seem to do anything. Following the Evolution of Combat update, the damage rate of the floor traps remained unchanged, effectively negating the need to bring healing supplies or food except in the case of extremely low level players. Re-spawn of the wall safe is mere seconds, making this activity a fast way to level up. With no failures and fast cracking (one attempt can take from 3 secs up to 10) one could make about 1500 experience points per minute (90k exp per hour). Realistically, it is much less (Around 20k/h)

Cracking wall safes appears to be one of the fastest ways to get uncut gems.

In an inventory of loot, you would get around 11 uncut emeralds, 11 uncut sapphires, 4 uncut rubies, if lucky and 1500 - 2200 coins. That is about 75k to 90k an inventory. Even though sometimes it is possible to gain as low as 30k an inventory because prices change.

An effective way to stay at wall safes for long periods of time is to use a Gem bag, as it can hold the gems leaving more room for food. However, Emerald Benedict the banker is nearby. Higher Agility levels reduce the damage a player receives for a failed attempt at cracking a safe.

Loot

 * 20 Coins (very common)
 * 40 Coins (common)
 * Uncut sapphire (quite common)
 * Uncut emerald (uncommon)
 * Uncut ruby (uncommon)

Loot Rates
(Based on a 1042 successful attempts sample)

- 20 Coins (399x) - 38.292%

- Uncut sapphire (115x) - 11.036%

- Uncut emerald (72x) - 6.910%

- Uncut ruby (44x) - 4.223

(Based on a 1521 attempts sample with stethoscope)

- Unsuccessful (278x) - 18.28%

- Successful (1243x) - 81.72%  (100%)

- Coins (1006x) - 66.14%  (80.93%)

- Uncut sapphire (125x) - 8.22%  (10.05%)

- Uncut emerald (78x) - 5.13%  (6.28%)

- Uncut ruby (34x) - 2.24%  (2.74%)

(Based on a 1656 success sample with stethoscope at thieving level 92)

- Uncut sapphire (170x) - 8.38%

- Uncut emerald (101x) - 4.98%

- Uncut ruby (53x) - 2.61%

Trivia

 * Wall safe cracking is not mentioned in the Skill Advance Guide.
 * When using the stethoscope to crack wall safes, it is possible to crack the safe by simply clicking it, this method will still cause your character to use the stethoscope. It is currently unknown whether clicking the stethoscope or not determines your chance of succeeding.
 * Wall safe cracking is a very helpful task in RuneScape. You're able to gain up to 90k thieving experience an hour as well as bringing in up to 310,000 GP an hour from the gems.
 * It has been suggested that a higher Agility level will increase your likelihood of getting better gems, more so than a higher Thieving level will. At this time it is unknown if this is true, however a high Agility level does appear to yield better results.
 * Uncut Diamonds were removed from the loot tables alongside a graphical update to the Rogues Den.