Setting alarm clocks in hostels?

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This may be the dumbest of dumb...but should I bring an alarm clock or use a watch alarm or something when I am staying in hostels?

I imagine everyone has certain times to catch trains so it must be standard and I'm assuming it isn't considered rude to set an alarm on your watch

Also is there a specific checkout time for hostels?

For example in Berlin the day I leave I wanted to take the Third Reich Tour which goes from 10 am to 2 pm but need a place to stash my pack, so could I leave it in my hostel locker and come grab it from 2-3 or do I have to remove everything by a certain time?

I'm a VIRG backpacker leaving next week so I may have some pretty basic questions...

Thanks to anyone who replies...