During exams Ravenclaws just prop their common room door open with a spare book so that students don't have to worry about solving any goddam riddles after studying all night.
Also, it is an unspoken rule that anytime ever someone doesn't feel like putting up with that door, they can just knock. Because 97% of the time there is at least one other Ravenclaw in the common room, probably studying, and Ravenclaws are all smart enough to understand that there is a time for learr and a time for crashing on your bed after spending + seven hours straight in the library. It's Ravenclaw lore that, once, a girl spent all seven years without ever having to answer a riddle.
Plot twist - that student was Helena. She did it just to p!ss off her mom.
