It is a gray machine installed on the wall at the Krusty Krab. It consists of an orange-brown clock on top which contains yellow numbers and hands. Below there are shelves used for employees to store their cards.
Technologically, it is a time-measuring machine used to determine an employee's tardiness or on-time arrival. Below the clock, there is a slot inside which one must insert their employee card into to activate the machine. Doing so will result in a robotic female voice stating the employee's on-time percentage.
Role in episode
SpongeBob, arriving at the Krusty Krab early, is waiting in front of this machine for the clock to hit 8:00am, the start of his shift, so he can immediately insert his employee card once the aforementioned time starts. He does so and his on-time percentage is at 100%.
Rather late to work, Squidward inserts his card into the machine, with his on-time percentage being 12%.
Later in the episode, just when the Tattletale Strangler is about to get revenge on SpongeBob when the two are alone at the latter's house, a majority of SpongeBob's friends throw a party for him for having a 100% on-time percentage.
Despite the Krusty Krab only having two employees, there are more than two employee cards placed in the machine's storage shelves.