Hello Patrick, Single actions only have a few points for adjustment but these are critical for them to function properly. They are a lot like upright actions, so some of the same things apply. Replace the keyboard cloths if they are worn or moth-eaten, and level the keys since you've got the rails off; check whether the knuckles need brushing before you reinstall the hammer rail. Reassemble the action when you've finished repairing the jacks; the hammers should rest on the rest/let-off rail, where the jack heights are adjusted for enough lost motion as to return freely. A neighboring key needs to be lifted from its center rail pin in order to remove a key, at least enough to adjust the rocker screws. Set the let-off or at least even it out, and check hammer pinning. Each hammer should bounce either 2 or 3 times before rest on a normal blow, and some actions have set screws on the flanges for this adjustment - otherwise, you may need to repin. Then set the back-checks (some of them may have gotten bent adjusting the jacks). Keep in mind that hammer pinning, checking and jack clearance are all that these single actions have for repetition. You may need to space hammers afterwards, which you can do with the action in place if you have long arms and make a tool. Mine is a length of maple with two metal strips protruding downward to grab the flange, and between them is a slot to clear the screw. It does not always work, so if you space them by sliding the action in and out, be careful of the soundboard spacer between the tenor and treble sections. I was referred some case repairs recently by another tech. on a very late home-refinished S&S square in good playing condition which sold for what would count as a very substantial price for any instrument, so this one shouldn't mind some regulation; this said, I think there are far superior squares to S&S's. Good luck, Clark
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