A few SMC comment code translations:

BB within a couple of log lengths and below live crown otherwise is a BT.  Tree is dead/dying.
BT generally upper third and still has live crown and likely will survive.
FB generally above dbh but not as far up as upper third.
FL within the last 1 to 3 years of growth depending on how much growth.
FT within the upper third and one is winning.  Lower would be a FB.
MT seems to me to be better suited for juvenile trees or at least in the upper third and no clear winner yet.  
SB shared base covers trees forked lower down below dbh.  We would normally call MS (multi stem).