1 - Line thickness 1 6 - Line thickness 6 A -Pencil Tool Z -Undo
2 - Line thickness 2 7 - Line thickness 7 S - Airbrush Tool Y - Redo
3 - Line thickness 3 8 - Line thickness 8 D - Line Tool  
4 - Line thickness 4 9 - Line thickness 9 F - Circle Tool  
5 - Line thickness 5 0 - Line thickness 10 G - Rectangle Tools