Hold the Door, Please
What’s your best guess, looking at this “hardish yellow foam”? It looks like the letter U or the letter C, but what’s the purpose of this thing? While this person was certain the item was baby-related, they didn’t have much else to offer other than it is made of some kind of hard foam.
Lots of things can be baby-related, but this one isn’t as directly related as the poster perhaps implied with their initial guess. This is a doorstop, useful not only for making sure kids don’t lock themselves in but for pets as well. In fact, if you have a door that likes to shut itself and you have a Roomba, this could come in handy for that purpose as well.