Linen tape is used to secure four small regimental buttons, as seen in this inside view. The knee band is sewn to the button and buttonhole stand, which overlap it. Not visible here is another button sewn to the knee band on the same side as the others.
Blocked by the buttonhole stand is another buttonhole in the knee band at the bottom of this image. Because the wool will stretch, the buttons and buttonholes are tight and hard to button at first.
Make sure to measure for button placement with the thickest stockings you will wear with the breeches. It's fine to transfer these measurements to the other leg, but ONLY if your knees are the same size. Mine are not anymore.
The convex front and concave back of the leg are obvious here, and the outside seam is also slightly longer than the inside. The marked buttons make this garment specialized, but attractive. Now all that is left is to finish the fall.