It is a black haircomb that contains three sides for one to brush their hair.
Role in episode
While locked out of his house, SpongeBob attempts to gain entrance by going through his bathroom's open window. During the process, he hears Larry going through his medicine and hopes he does not touch his special comb. While examining himself in the mirror, Larry deems himself good enough to eat, but thinks he could use some teeth whitening, so he rummages through SpongeBob's medicine cabinet for toothpaste and then gets distracted by the bizarre nature of the latter's haircomb.