Cardboard box as a carry on?

I’m going to be flying for Thanksgiving and would like to avoid paying to check a suitcase to carry 2 days worth of clothes. I have a cardboard box that meets the airlines size requirements for a carry-on, but I am not certain if this is acceptable as “luggage”. Has anyone done this before? Does it need to be sealed, or should it remain easily opened in case it should be searched? thanks!