Taper pin reamers are designed to prepare the hole for taper pins. The cranks attach to the spindle via a common square taper, cotter or splined interface. Tools with an R8 taper are inserted directly into the machine's spindle. These overblown registers can be tuned by using different degrees of conical taper. Erlenmeyer flasks have wide bases, with sides that taper upward to a short vertical neck. These days, ground glass joints can be precisely ground to a reproducible taper or shape. Its planform changed to a constant taper from root chord to tip chord. Roots that curve apically provide increased support compared to those which have a fixed taper. Better machetes will also have a slight distal taper. These bulbous structures taper smoothly to a point. The cavities taper down toward their ends and overlap. These swords took on a much more acute distal taper and point. Adjusting the angle of the bore taper controls the frequencies of the overblown notes (harmonics). Theobald Boehm described the shape of the taper as parabolic. At the bow, all of the planks taper to butt the stem.