Why some stubs called reflector, for example 2*F0 reflector?

[Terminator3]

I can't understand, is it actually reflects some? I thought quarterwave stub makes short at it's F. But in few designs where harmonics involved, they call them reflector at n*F0.

 

[chuckey]

With a traditional Yagi aerial, stubs in front of the actual dipole are called directors, those BEHIND the dipole are called reflectors. they increase the forwards directivity and reduce the pick up from behind the dipole.
Frank