400 
LOGGING 
points, and for towing. They are built in many forms and are 
called sheer booms when used to confine logs for storage purposes 
in given channels and towing booms when used to impound logs 
for towing purposes. They are again designated as limber and 
stiff booms according to their manner of construction. Both 
sheer booms and towing booms are often of the same pattern and 
are known as the "plug" boom, "sheep-shank" boom, "chain" 
boom, "bracket" boom, "fin" boom, and "barge" boom. The 
first three are single-log limber booms, the names referring to 
the manner of attachment one to the other; the bracket boom is 
DOG AND CHAIN 
CLEVIS AND RI.NG 
Fig. 140. — The Methods of fastening Boom Sticks with Chains. 
a stiff boom several logs wide; and the fin and barge booms are 
either stiff or limber. 
Plug booms, also known as "plug and knock down" booms, 
have logs fastened end to end with short pieces of rope or withes 
the ends of which are passed through holes bored in the ends of 
the boom and securely fastened by plugs. 
Booms of this character are serviceable as a makeshift when 
stronger fastenings are not available. 
Sheep-shank booms are temporary booms fastened together by 
rope, a half hitch being made around the ends of the logs. They 
are used for repairing breaks in other booms where rope is the 
only equipment available. 
Chain booms are the common form of limber boom in use to- 
day. Short chains are used to connect the logs, and are fastened 
in several different ways: (1) by a chain and dogs; (2) by a ring 
and toggle ; (3) by a clevis, making an endless chain. The latter 
