Cover shapes in background with filled shapes in foreground

I would like to draw shapes using the polyshape function, e.g. by writing:

x0=[0 0 200 200]; y0=[10 0 0 10]
    SquareShape=polyshape(x0,y0)
    plot(SquareShape)
    hold on
    ElmX=[0 5 10 20 25 30 40 40 60 70 85 95]
    ElmY=[12 -2 12 -2 12 -2 12 -2 12 -2 12 -2]
    plot(ElmX,ElmY)
    hold on
    x1=[10 10 20 20]; y1=[10 0 0 10]
    SquareShape=polyshape(x1,y1)
    plot(SquareShape)

but when I run the routine it generates transparent pictures, whereas I want the last shape created last (in this case the one created in the line before last) to cover the surface beneath itself.