Prop direction
Not as daft a question as it first seems. There are some subtle differences between the front and back of a propeller.
Most of us know that a wing works by a combination of air deflection and the creation of a low pressure over the top of the wing due to the longer distance the air travels over the convex curve of the wings surface thus sucking the wing upwards, well a propeller basically works in the same way so when you look at the prop, the face that has the convex surface is the front and if that sounds a bit complicated then just look which side the numbers are printed on and thats the front!
