I do this for a living (finish carpenter) and the replies are mostly pretty good. For the 25 a week I tend to cut, I wrap a bunch of masking tape all the way around the bottom of the door and up about 6"
Then I measure up what I want to cut (yes, leave a little room for air) so typically about 1". I use a drywall square or level and scribe the line with a utility knife on the top side,. Then I cut with a circular saw using my finger as a guide on the bottom of the door. Then I use a piece of sand paper to bevel the edges a little. Then I spray with some spray can lacquer to seal it up. Remove tape and re-hang door.
If I can cut in the same room, takes about 4 minutes start to finish.
Brew
Then I measure up what I want to cut (yes, leave a little room for air) so typically about 1". I use a drywall square or level and scribe the line with a utility knife on the top side,. Then I cut with a circular saw using my finger as a guide on the bottom of the door. Then I use a piece of sand paper to bevel the edges a little. Then I spray with some spray can lacquer to seal it up. Remove tape and re-hang door.
If I can cut in the same room, takes about 4 minutes start to finish.
Brew

