You can block a number from a landline by using a call blocker device, contacting your phone service provider to activate call blocking on your line, or manually blocking the number through your phone's settings if it has that feature. A call blocker device can be connected to your landline phone and programmed to block specific numbers or types of calls. Your phone service provider may offer block calls on landline for a fee or for free depending on your plan. Some landline phones also have a call blocking feature that allows you to block numbers manually.
We used to let the phone ring if we wanted to take no chances until Caller ID came out; after that, we could see who was calling and be more selective about who to leave ringing. Bonus tip: Leaving it off the hook, or unplugging it, results in a peaceful night.