Patches are often used on jerseys as part of the uniform for baseball players of all ages. They come in many different types, like letter and numbers or team logos and awards. Patches are also used to decorate jerseys as a regular part of a wardrobe. Either way, you will want to attach the patch to the jersey correctly so that it is well placed, neatly sewn and securely held. You do not need a sewing machine to sew patches on, as they can be sewn by hand.
Place a piece of double-sided tape onto the back of the patch and press it in place on the jersey. This will keep the patch still so that it does not become crooked before it is sewn.
Thread your needle with thread that matches the embroidered edge of the patch. If the patch does not have an embroidered edge, match the thread color to the flat edges. Knot the end of the thread to keep it from slipping through the fabric and un-doing your stitches.
Hold the jersey up with one hand and use the other hand to poke the needle through the inside fabric of the jersey and up through the edge of the patch.
Poke the needle back down into the patch, close to where you pulled the needle up. The closer your stitches are to each other, the better the patch will look, and the stronger it will hold. Do this all the way around the patch, removing the double-sided tape once you have stitched half-way around the patch.
Knot the end of the thread after your last stitch--which should end inside the jersey, not outside--and cut the excess thread with scissors.