The door a criminal will get into is the front door. Now hold on, you may be thinking, wouldn't they go for the back door? No! 99% of home invasions happen when you leave your own front door unlocked!
To protect your front door from criminals you plan to fill it with heat (ひ). Oh yeah, we're gonna Kevin McCallister this.
Currently there are no similar looking kanji which exist in the WaniKani learning system