When your leather boots are too tight on your calves, you can add an elastic gusset to make them more comfortable. You can get away with using any color elastic if you wear your pant legs over your boots, but use elastic in a color that matches the boot leather if you wear your boots outside your pant legs or with a skirt. You will need to hand sew the gusset in place.
Measure three inches down the inner seam of each boot, from the top edge. Cut, using the razor knife or carpet shears, the three-inch length you just measured.
Stretch the elastic, and use the stretchiest direction to run across the boots. Do this by making a small mark in the center bottom edge of the elastic and then cutting up to each upper corner. The remaining will form an upside-down triangle.
Sew all the way around the edges of the elastic triangles using the zigzag sewing machine. This will finish the edges and help prevent fraying.
Thread the hand-sewing needle, and position the elastic in the boot with the top edge of the elastic aligned with the boot's top edge. The elastic will overlap the cut edge of the leather by 1/2 inch. Begin sewing from inside the boot at the bottom of the triangle.
Poke the needle through the elastic and the leather. The needle should come through the leather 1/8 inch from the edge. Move the needle over 1/4 inch from the leather's cut edge and poke back through the leather and then the elastic.
Move the needle 1/8 inch up on the elastic, working toward the boot top, and poke the needle back through the elastic and then the leather. Continue making these small stitches over and over until you reach the leather boot top. Repeat on the other side, and then do the other boot.
These directions are for adding an elastic gusset to a mid-calf boot, like a cowboy boot. Use a longer elastic piece for knee-high boots. Use a wider piece of elastic if the three-inch addition is not enough to make the boots comfortable.
It will take a fair amount of finger strength to poke the needle through the boot leather. Use a thimble on your finger to push the needle through.