but the aperture relationship is the same in fig7 the envelope back acts as guides for the movement of the insert sheet 42 referring to fig8 and 10 there is illustrated the use of my stencil to produce a shadow effect on the numeral 1 an envelope 41 with an aperture 42 in the shape of numeral 1 has an insert sheet 43 disposed therein also having an aperture in the shape and size of the numeral 1 of the envelope a tab 45 is attached to the insert 43 and projects through the open top of envelope 41 for manipulation of the insert 43 a stencil numeral 1 on a sign board 44 of fig9 is made with the two apertures registered the color of the image as shown by horizontal lines in fig9 the operator next holds the envelope 41 on the same place on the sign board 44 but moves the insert 43 to the left and the right edge of the insert aperture is the line 46 this movement of the insert 43 covers up a strip of the right part of the stenciled image in fig9 if now a different color ink or paint is applied the part of the numeral 1 not covered will be a different color as shown by the diagonal cross hatch lines in fig1 by careful selection of the two colors a shadow effect is achieved illustrated in fig1 is an envelope 47 having apertures in the front and back in the shape of a fanciful design 48 an insert sheet 49 also has identical pattern of apertures and has lesser dimensions than the envelope 47 so that it can be moved within the envelope to cover up selected portions of the.