On timetables under the "capacity" column you will find the number of yards as well as a designator (BCKOPTWXYZ). Mike Gerenday helped unravel the mystery to some of these designators:

B = Bulletins
C =
F = Flag Stop
J = Junction
K = Standard Clock
O =
P = Telephone
R = Train Register
T =  
W = Water
X =
Y = Wye
Z = Track Scales