Kevin, The butt-felt below the buckskin knuckle on an upright hammer butt maintains the position of the jack through the arcs of the two parts up until let-off, which should occur at the intersection of the two cloth cushions (sometimes which are separated by a little of the wooden moulding). The upper cushion doesn't bear upon the jack as much, or even the same as the lower, kind of a slap felt upon its return; they aren't always different thicknesses, though. I assume it's cheaper to install two pieces rather than to stretch and clamp a single piece of cloth. The profile is much gentler (at least in most modern actions) than the various grand knuckles with fairly compressed cloth under coverings, so there couldn't be much advantage to this practice in uprights, anyway. Regards, Clark
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