Mosvalve
If you think about it a shield should be place behind you. The mic is facing you and picking up the room behind you not in front of you.

It depends on the problem you are trying to solve.

If you have a source of noise directly behind you than a baffle of some sort does quite a bit of good. I don't think a shield will be large enough, or dense enough to do anything.

These shields are intended to provide a more "Vocal Booth" like experience, without the expense (and size) of a vocal booth. They will diminish the energy reaching the microphone from the rear, which will tend to deaden the recorded track. Depending on the room the effect can be subtle or quite obvious.

This does not mean you don't need baffles (aka gobos). These are invaluable in the rooms where many of us end up recording (myself included!). And they can be really handy in a well thought out, well behaved space too!