Jet Striking a Plate

I have been introduced to momentum in fluid flow recently and was covering a jet striking a plate (stationary, inclined and moving away/toards the jet). In each of these cases the resource I was working through mentioned that the normal velocity to the plate = 0, however, they didn’t say why (presumably because it is obvious). However, I don’t understand why this is the case. I came up with one reasoning, but I am sure it isn’t correct:

Similar to flow modelled using streamlines the development of a stagnation point means velocity is 0 at the point directly centre of the object.

Why I don’t think this is correct is because it doesn’t explain why the normal velocity = 0.

I am probably fogetting something trivial about momentum.

For reference here is the image I am talking about:

Where Vn is the normal velocity of the jet to the plate.

Any help would be much appreciated. Thanks.