Vertical Shear Effect

Hi

I'm try to shear an object (it's the ribbon in the photo below). When I select horizontal in the options panel, i can shear it to the angle selected, when I select vertical (which is the shear effect I want), nothing happens, nada, zilch. 

I would like it so the bottom left of the ribbon stays in position, but the right hand side is raised slightly on the vertical axis. Whatever value I put in nothing happens?

Am I missing something here? 

Thanks,

Paul.