Pits

Pits are a type of trap that appears in a few select levels. All pits have in common that once a robot falls in, it cannot be recovered.

There are several types of pits in the game: In the game canon, there exists an entire department dedicated to "building" bottomless pits.
 * Pits of molten metal, as seen in Crossover Story
 * Spike pits, as seen in I Am The Wall Rush
 * Bottomless pits, as seen in Gravity Fails and Exitus Machina

Trivia
In one of the Announcer's voice clips it is implied that employees of Death Trap Incorporated will regularly throw objects into the bottomless pits of the aptly named "Bottomless Pit Department" to hear when they arrive at the bottom - much to the annoyance of the company, which considers it a waste of time as well as of objects.