Hammer don't want to build mesh with the snapped grid

Please anyone help me ?

Since maybe 1 hour, i’ve a problem with my hammer grid.

When I build mesh, the limitation of the mesh don’t want to snap to grid.
*
Je suis français.*

SCREEN :

http://image.noelshack.com/fichiers/2016/31/1470429726-sans-titre.png

Press “Map” up the top and press “Snap To Grid”
or press Shift + W

Hooo Thanks a lot man !! I love you !