20 through eight strip 80 are not shown however similarly to first strip 10 each of the second strip 20 through eight strip 80 are also formed from curved plywood and comprise a top surface and a bottom surface each of the second strip 20 through eight strip 80 also comprise a concealed flap a first raised portion a middle portion a second raised portion and an exposed flap for example fifth strip 50 comprises concealed flap 50 a first raised portion 50 b middle portion 50 c second raised portion 50 d and exposed flap 50 e etc further in fig1 through fig4 first strip 10 through eight strip 80 are shown as having substantially identical size it is not critical that first strip 10 through eight strip 80 be of a substantially identical size they can slightly differ in size viewing again fig1 the top surface of concealed flap 10 a is positioned adjacent to the bottom surface of second raised portion 50 d the top surface of concealed flap 20 a is positioned adjacent to the bottom surface of first raised portion 80 b the top surface of concealed flap 30 a is positioned adjacent to the bottom surface of first raised portion 50 b the top surface of concealed flap 40 a is positioned adjacent to the bottom surface of second raised portion 80 d the top surface of concealed flap 50 a is positioned adjacent to the bottom surface of second raised portion 40 d the top surface of concealed flap 60 a is positioned adjacent to the bottom surface of first raised portion 10 b the top surface of concealed flap 10 a is positioned adjacent to the.