Once you have mastered knitting the basic beanie, it is time to branch out to brimmed hats. There are many ways to stiffen the brim of a knit hat, including changing to smaller needle size, doubling the yarn in the brim, using starch, doubling and folding over the brim, or inserting a supporting material into a knit pocket of the brim. Knitters use a range of stiffeners, including wire, cardboard, plastic mesh, or plastic canvas. Plastic has the advantage of being light, washable and flexible.
Trace the brim of your hat onto the plastic canvas with marker. For a baseball or newsboy type hat, trace a semicircle. For a hat with a circle-shaped rim, trace a doughnut shape.
Cut out the brim support slightly smaller than the outline you made.
Pin the brim support to the hat and trim it to size.
With your knitting needles, pick up stitches at the edge of the underside of the brim.
Reversing the pattern you used to knit the brim (decreasing where you increased), knit another brim over the support.
When your knitting has reached the base of the hat, use your larger needle to pick up stitches at the underside of the hat where it meets the brim. The number of stitches should equal the number of stitches left on the smaller needle after you finished knitting the second brim.
Do a three needle bind-off with the stitches you picked up, enclosing the support inside your brim. Remember to remove the pins as you seal up the brim pocket.
Plastic for brims can be cut out of gallon milk jugs.