Your instincts are right, I'd never grant physical access to me and my home just because somebody I wasn't expecting knocked on the door. It's not on you, if they don't have your phone number or your email and it's that important they should leave a note. I recently moved into a place without a peephole in the door too. And last month I had an unexpected knock on the door that set my heart racing. No, I didn't answer. They didn't come back, thank God, or my anxiety would be sky-high too. I thought I'd eventually get around to installing a peephole, and now you've inspired me to begin a preliminary search. At first glance, it might be easier to do than I thought. Might be worth it. If you want to, and you are renting, I have some advice for you. Don't ask the landlord. Most will say no, and they won't let you do it either. Landlords hate spending money and they won't give permission because of the chance it'll be done improperly and they'll have the cost and headache of replacing the door. If you don't do anything, zero cost and risk for them. To hell with your problems. Just do it, buy quality parts, and get a handyman to do it quickly before anyone notices. Then play dumb. Offer to have it removed and patched up and then just don't do it if they call your bluff.