Cut the footboard of the twin bed in half vertically. Mount one half of the footboard to the side of the headboard by securing it to one of the legs with screws. The screws should be inserted through the back of the materials. Add the second footboard half to the other leg of the head board to create one solid full-size headboard. You can add wood trim to the headboard to change its appearance.
You can build an entirely new full-size headboard by cutting the twin-size headboard and footboard into square pieces. Remove the legs from the original twin-size boards to use for another project. The squares of wood should be well sanded to prevent any injuries. Mount the pieces to a piece of medium density board or plywood with wood glue and screws. Hang the completed headboard on the wall behind the bed.
Take the headboard and footboard apart. Arrange the largest pieces of wood to create the shape of the new headboard. Attach the wood together using metal brackets and screws. Spray adhesive on the wood surface and adhere polyfiber batting to the front of the new headboard. Cover the headboard with an upholstery or cotton fabric to create a soft padded surface for your full sized bed. Sew decorative trim around the edges of the fabric for a finished look.
Cut the headboard pieces to create a shaped headboard for the full sized bed. Use a saw to cut curves and decorative scroll work for an elegant headboard. Give the sanded wood a solid coat of pastel colored paint or an antiqued appearance with gold paint. Add a padded center to the piece using velvet or upholstery cloth. Hang the decorative headboard on the wall behind the bed securely using brackets.