The thermal detonator is a weapon in the Jedi Knight games. It carries the same qualities of a hand granade as well as having a few other features.
The thermal detonator is a medium range explosive, damaging any enemies close enough to it when it explodes. It can also damage or kill the player if they are close enough. It should only be used for killing enemies at a distance or in harder-to-reach areas such as up on a ledge. There are two modes for the thermal detonator. Primary mode is an impact detonator, causing the projectile to explode on contact with anything, including walls and floors. Secondary mode is a delay detonator. This causes the thermal detonator to explode only after a few seconds, or if it comes into contact with an NPC (this includes non-combat characters such as civilians). Thermal detonators can be aquired by collecting them one at a time, or collecting detonator belts, which carry three detonators. They can also be taken from killed Grans, as they are the only enemies in the games to use them.
Thermal detonators are actually quite weak compared to other explosives, sometimes requiring two or more hits against standard humanoids for a kill. Nonetheless, since detonators can be bounced around corners in the timed mode of attack, they remain useful for weakening or killing enemies without requiring the player to break cover.
In level 2; "The Lost Disk", in the large room containing three Grans out in the open found adjacent to the rooms where the Gammorean guards are first encountered, there is a belt of thermal detonators partially inside the left wall adjacent to the hallway leading to the cargo room. It is too high to get without cheats. This is caused by the detonators being placed in part of another room (a dark secret area near the end full of shield recharges) that intersects with another area. LucasArts cheated much of the level design where impossible spaces were created. Sectors that partially intersect can still be rendered and explored independently. It would be impossible for these levels to exist in the real world.