Daniel, It sounds as though the "rebuild" did not include a new soundboard?  Anyway, if you like the sound and it's not buzzing, just let it be.  No, you can't shim from underneath, you would need to de-string remove the plate and shim the cracks. A lot of work, especially for an upright.  Then again, if it starts to buzz, then off to work you go if you think it's worth it! My 2 cents Paul <table width=100%> <tr valign=top> <td width=40%>"daniel carlton" <hacicspe@gmail.com> Sent by: pianotech-bounces@ptg.org 02/15/2008 01:08 AM <table border> <tr valign=top> <td bgcolor=white> <div align=center>Please respond to Pianotech List <pianotech@ptg.org></div></table> <td width=59%> <table width=100%> <tr valign=top> <td> <div align=right>To</div> <td>"pianotech mailing list" <pianotech@ptg.org> <tr valign=top> <td> <div align=right>cc</div> <td> <tr valign=top> <td> <div align=right>Subject</div> <td>soundboard on my 1890's Knabe upright</table> <table> <tr valign=top> <td> <td></table> </table> hey techs   i've got a rebuilt (rebuilt 2 or 3 years ago) 1890's Knabe upright. nice warm, woody sound, and it's already been used in a few recordings. i'd like to have it sound nice for many more years. i do have one concern. i've noticed a crack or two in the soundboard, and it bums me out to have a rebuilt, beautifully sounding piano with a crack in the soundboard. now i did a few shims at nbss on grands we were rebuilding, but never any uprights... and in the following post <a href="https://www.moypiano.com/ptg/pianotech.php/2006-January/184497.html">https://www.moypiano.com/ptg/pianotech.php/2006-January/184497.html</a>, David Ilvedson says you can't shim from behind. so my question is can anything be done to fix the cracks?   as always, any help is greatly appreciated.   thanks   daniel carlton