A while back I stumbled over something called "Everyday matters". It's a group devoted to drawing and art and that get a challenge every week for something new to draw. For me it's perfect, I get inspiration and a push to work on drawing every week.
Last week was my first time and the theme was "draw a lock". I found a padlock that I use for the gym, and it has the keys fastened with a rubber band, which was also very good practice to draw.
Of course I couldn't do just one :)
(Shown in the order I drew them, the top one first, and the combination lock last)