To do this repair you will have to de-tension the strings enough to un-bridge, un-hitch them and thread them on a wire to hold them in order. There should be two to four screws to secure the bridge (or apron) to the soundboard. Remove these screws, and if the holes in the apron have been damaged get slightly longer or slightly larger screws. Dry fit the apron to the board and using a piece of string (fishing line is better), stretched from the agraffe pin to the hitch pin, check that the bridge is slightly higher than the hitch pin at each end of the bridge. If this is not the case you can do two things. One is to wedge the bridge up slightly so the glue sets at a slight upward angle or two cut a piece of veneer or similar thin wood and insert it between the apron and the soundboard. When all is fitted and nice remove the apron (and shim), put glue on the apron, shim and soundboard and secure the whole with the screws and wait until the next day to replace and tune the strings. It would be nice if you have an assistant for this job or you will be getting your exercise running around the piano. Not a difficult job, just one requiring planning each step and being neat and orderly. newton
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