Welding Kits have a lesser known function in that they can be used to "break" the sliding lock on doors from the outside of a room. Since such doors can only be locked by the player themselves, this only applies to rooms that have more than one door, such as the Kitchen or the Engine Room. Once a lock is broken in this way, the door can never be re-locked.
The player is advised to use the tool first in order to the other items needed, as the noise generated will attract the monster to the sub's bay and the player will need to leave the area to search for more items anyway. If however the player has all the items required before applying them to the submarine, the welding kit should be applied last, as the monster will be attracted the slowest this way.
Unlike a lighter, a welding kit effectively has infinite fuel and is thus a decent alternative to a flashlight. However, a welding kit's flame will only stay active for a few seconds before it must be activated again, making it less reliable.