Can you use thieves' tools to construct locks and traps, or do you need heavier tools? [duplicate]

So in D&D 5th edition, one can make a character with a background, e.g. a guild artisan who does locksmithing. Obviously a locksmith is very good at picking locks, even if he has no levels in the Rogue class. In this example, consider a guild artisan locksmith who becomes a cleric of Gond, god of craftsmanship.

The PHB doesn't get very specific, but a non-Rogue guild-artisan locksmith character who starts out might get (10 pounds of) "tinker's tools" or (1 pound of) "thieves' tools."

For adventuring, you could say that the locksmith just takes thieves' tools because they are lighter to carry, but probably that wouldn't be enough to construct a new lock, much less a new trap.

Assuming that the locksmith-adventurer plans to construct new locks (and possible new traps) while in a dungeon, presumably he would need to bring along lots of spare parts, and thus he would have to carry a tool kit at least as heavy as "tinker's tools."

Given earlier questions such as: Do you HAVE to have Thieves tools in order to pick a lock?

I suspect that the rules are not very precise about whether player-characters with a locksmithing background can construct traps while in a dungeon. From my guesstimate, I would say that they would need to negotiate with the DM to make sure the action is allowed in that DM's campagn.

Am I missing some clear rule on lock-and-trap construction, or did the rule designers just leave it open to interpretation?

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There is a simple answer with regards to the basic lock and the hunting trap, both listed in the PHB on page 152. Since these are nonmagical items, a player proficient with the correct artisan's tools can use the Crafting rules under Downtime Activities (page 187) to craft these items.

I'm not going to reproduce the whole section here, but a player could craft a hunting trap in a single day for a cost of 2 gp, 5 silver, and a basic lock in 2 days at the cost of 5 gp. This would require artisan's tools of an appropriate variety rather than thieves' tools. If you read the description of thieves' tools, it seems clear that they couldn't realistically be used to construct anything.

As far as any more complicated locks or traps are concerned, it's up to you. Personally, I would allow a player who took proficiency with locksmith's tools to construct more difficult locks, but it would take longer and be more expensive than creating a basic lock.

I'd be a little more worried about the idea of letting a player build arbitrary traps of their own invention, since it seems like it could be a bit gamebreaking. I also have no idea which artisan would be a professional trap-maker.

Either way, I wouldn't let a player construct anything more than a makeshift lock or trap while in an active, hostile dungeon. I'd say that materials, tools, some sort of workbench, and possibly even a lack of evil monsters in the near vicinity would probably be required for this kind of work. Note that the crafting rules in the PHB do have a rather fuzzy sentence to similar effect.

Xanathar's Guide to Everything provides optional mechanics for tool proficiencies, including a special use of thieves' tools for those that are proficient (p. 84):

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. [...]

There's more, but it seems pretty clear the answer is an emphatic YES, limited by what you have on hand or can scrounge. Looking through the equipment table inspires a few simple ideas:

• A portable ram and a length of chain could make a really brutal one-use trap for a doorway or staircase. (think "Home Alone")
• 10 javelins and the Mold Earth/Minor Illusion cantrips.
• A hunting trap, a chain, and some pitons.

XGtE also has a whole section on traps (pg 113) with a bunch more ideas. Some are impractical given time, labor, or material limits, but for example a small party should be able to do a lot to help a small village fortify itself against a large orc band or something.