With a small serrated knife, gently saw lengthwise through the center of 4 of the graham crackers along the perforations (you will have one extra piece). From 2 more graham crackers, cut the barn roof support sections, using the pattern (you will not use the trimmings). Gently saw 3/4 inch from a short side of 2 more of the graham crackers, making 2, 3 1/2-inch long crackers (you will not need the 3/4 inch pieces). Cut 2 of the pretzel rods into 2 1/4-inch pieces (you will have extra pretzel pieces). Set all pieces aside.
For the frosting:
In a small bowl stir together the powdered sugar and the 1 cup canned frosting until combined. Transfer frosting mixture to a sturdy resealable plastic bag. Snip off a small portion of one corner. Or, spoon frosting mixture into a pastry bag fitted with a small round tip.
To assemble the silo:
Pipe a line of frosting down the side of the cardboard tube. Press a lengthwise-cut cracker section into place, flat side in, as shown in photo. Repeat with 4 more sections to cover the tube. For the dome, cut the cupcake horizontally in half (you will not use the bottom half). Frost top half with additional canned vanilla frosting. Coat with sprinkles. Place on top of the silo. Set silo aside to dry.
To assemble the barn:
Lay a graham cracker rectangle and a roof support section on a work surface. Slide long edges together to form the barn front. Frost one side of a cut 3-1/2-inch-long graham cracker, and press it against the barn front. Frost one side of a cut 3-1/2-inch-long graham cracker, and press it against the barn front to hold the pieces together. Repeat to make the barn back. Pipe a line of frosting on the short ends of the graham cracker rectangles into place for the walls. Hold the walls in place with glasses. Allow to dry 1-1/2 hours.
To assemble the roof:
Pipe frosting along edges of roof support sections and walls, and press two lengthwise-cut graham cracker sections against the frosted edges of the roof supports to form the roof peak. Use the remaining two graham cracker rectangles to finish the barn roof.
Decorating the roof:
Pipe a line of frosting along the peak of the roof, and press the whole pretzel rod into place. Allow to dry 30 minutes. Pipe lines of frosting onto the roof; press thin wheat crackers into place, forming shingles. If desired, make barn doors by attaching sections of a chocolate graham crackers to the barn with frosting. Outline the doors with additional frosting and pretzel sticks. Makes 1 barn and 1 silo.