Thieves' Tools

Thieves' tools encompassed a wide array of equipment that aided a prospective rogue during their illicit activities. Many of these items were hand-crafted by the individual who intended to use them, but some were available through local guilds or specialty shops.
This set of tools includes a small file, a set of lock picks, a small mirror mounted on a metal handle, a set of narrow-bladed scissors, and a pair of pliers. Proficiency with these tools lets you add your proficiency bonus to any ability checks you make to disarm traps or open locks.
Perhaps the most common tools used by adventurers, thieves' tools are designed for picking locks and foiling traps. Proficiency with the tools also grants you a general knowledge of traps and locks.
Components. Thieves' tools include a small file, a set of lock picks, a small mirror mounted on a metal handle, a set of narrow-bladed scissors, and a pair of pliers.
History. Your knowledge of traps grants you insight when answering questions about locations that are renowned for their traps.
Investigation and Perception. You gain additional insight when looking for traps, because you have learned a variety of common signs that betray their presence.
Set a Trap. Just as you can disable traps, you can also set them. As part of a short rest, you can create a trap using items you have on hand. The total of your check becomes the DC for someone else's attempt to discover or disable the trap. The trap deals damage appropriate to the materials used in crafting it (such as poison or a weapon) or damage equal to half the total of your check, whichever the DM deems appropriate.

Activity	DC
Pick a lock	Varies
Disable a trap	Varies

Mechanics & Inner Workings

Thieve’s Knowledge

Thieves are experts at finding valuables and disarming the traps that often guard said valuables. Such a skill might have been learned in order to survive the streets of a city or during a particularly rebellious phase of life. However the skill were learned, they come with knowledge few others will have. A proficient thief will know

• Contacts in the criminal world, including a fence (someone who buys stolen items)
• How to gain information on a target through bribes, tailing, or deceit
• How to find hidden valuables
• Where to look for traps
• How to spot a rich target

When a player who is proficient with thieve’s tools is attempting any action that involves the knowledge above, I always let them add their proficiency modifier to their skill check. I do this to extend the usefulness of the tool and account for the knowledge a proficient thief would have. It is a great way to make tools a more important part of the game, and I highly recommend it!

When to ask for a Thieve’s Tools skill check

There are many situations in which you might allow players to add their thieves’ tool proficiency to a skill check roll. If the player is doing any criminal activity or attempting to learn about a target through sneaky means, it is likely they should be adding their proficiency. Some examples of when I might ask for a thieve’s tools skill check are when a player:

• Attempts to stealthily open a locked door or window
• Disarms or sets a trap
• Attempts to gain information using questionable means
• Investigates a room for a hidden safe or stash

Even though a few of these do not directly include the use of thieve’s tools (such as the gathering of information) I take into account what a proficient thieve would know. Tools imply knowledge, make sure to take that knowledge into consideration.

Perhaps the most used tools in D&D, thieve’s tools are used to pick locks, see around corners, disarm traps and stealthy commit crimes. Those with proficiency in thieve’s tools are ex-criminals, assassins, and rogues. These tools are not for common, law-abiding citizens. Players with proficiency in thieve’s tools will also have contacts in the criminal world and will likely have other nefarious knowledge as well.

Thieves' Tools

Item type

Tool

Rarity

Common

Weight

1 lb.

Base Price

50 gp

Raw materials & Components

A set of Thieves' Tools contains:

• a small file
• a set of lock picks
• a small mirror mounted on a metal handle
• a set of narrow-bladed scissors
• a pair of pliers

For thieves’ tools there are three additional abilities that proficiency grants.
Firstly, you gain knowledge of traps. While Xanathar’s Guide doesn’t specify precisely how this knowledge benefits you mechanically, it seems clear that you should be able to apply your proficiency in thieves’ tools to any checks made to understand or know about traps or areas famous for their traps.
Alternatively, if you would already be adding your proficiency bonus to such a check, you may wish to ask your DM if your proficiency with thieves’ tools can grant you advantage on the roll.
Your thieve’s tool proficiency also allows you additional insight into the process of searching for traps. You know how traps are put together, so you’ve learned to recognize their telltale signs, such as what the floor looks like when it’s on springs or how to listen for the ticking of clockwork.
Again, Xanathar’s Guide doesn’t specify the mechanical benefit, but just like above I recommend being able to add proficiency, or possibly gain advantage on the check.
Lastly, Xanathar’s Guide to Everything grants characters that have proficiency in thieves’ tools the ability to set traps in addition to disabling them. When you short rest, you can create a trap with items you have with you. After making an ability check with your thieves’ tools your roll becomes the DC that someone else has to beat to be able to discover or disarm your trap.
The trap’s damage is determined by the materials you had when crafting the trap. If you use a poison or a particular weapon then that will determine the damage. Alternatively, the trap might deal damage equal to half your earlier ability check. It’s up to the DM either way.
A trap that simply drops a heavy object on someone’s head might deal damage equal to half your check, while a hidden crossbow that fires when someone opens a door might simply do damage equal to its normal weapon damage.

Additional Uses for the File

A small metal file, in addition to its use in disarming traps, can be used to weaken or break metal structures such as jail bars, the axles of wagons and other carts, metal railings on balconies, and staircases, or the hinges of a door/trapdoor.
You can therefore use a file to commit small and subtle acts of sabotage that if done with magic or brute force would be much more easily detectable.

Additional Uses for the Lockpicks

Lockpicks are pretty much only useful for picking locks. However, you could also use your lockpicks to jam a lock by intentionally breaking the pick off while it’s inside. This may require the metal file, or your DM may rule that you can use brute force.
This can be handy as it makes the lock unopenable, and unpickable, forcing anyone who wants to get through the door to noisly break it down (which may take a few rounds depending on the door).

Additional Uses for the Mirror

While you may be tempted to use a mirror to bypass the Medusa’s gaze, in truth you’re better off buying a dedicated and large mirror for this.
You may also want to reflect sunlight to attack a vampire, but reflecting light like this is often more difficult than it sounds, and will only ever possibly be helpful when you are fighting a vampire inside a building when it’s daytime outside, and sunny, and are already close to a window or the outside. There will probably be easier ways then a small mirror in those scenarios.
The thieves’ tools mirror, mounted on its metal handle, is best for subtly peeking around corners, or through windows. It can also be, in rare cases, used to grant the magic user of the party line of sight to their target.

Additional Uses for the Scissors

The scissors are simply scissors. While situations where you can use them creatively may appear, it’s unlikely that they will be the best solution to an obstacle. Combined with Mage Hand, your DM may allow you to use them to cut small ropes at range, which could disarm or set off an extremely simple trap.
Anything more complex than this would require being an Arcane Trickster; they can use their specialized Mage Hand to fully use the thieves’ tools to disarm traps and pick locks.