heres what i did:
1.Open up image of Car
2.Create new layer on top (blank with no fill usually checker)
3.select magnetic lasso tool
4.trace around car but making box selections
This will give you your line
5.once line/box is selected,select Edit at the top -> Fill (in black)
Alternative is to use the line tool and set your thickness.
I can do a tutorial if people are confused,infact might be easier lol