Taking off a few millimetres from the bottom of a cupboard door?

My woodwork teacher told me use my planer to take off a few millimeters off the bottom of my cupboard door, but how do you know if you are planning perfectly straightly? I used a set square on the side of the door to measure ( assuming it was 90 degrees). And a ruler to measure across. I put a spirit level on top to see if it was flat, not if it was horizontal with the ground.

What is a VPN?

VPN is (Virtual Private Network) were first used by companies to enable their employees to securely access internal systems such as email remotely (e.g. from home or while on business trips). Today they are increasingly being used for personal use by individuals to protect their privacy while online in public places (e.g. when using the wi-fi connection in a cafe) or in a country where the internet is censored / blocked (e.g. China, Saudi Arabia…).