A
gear case, also known as a
chain case or
chainguard, is an enclosure for the
bicycle chain and
sprocket assemblages commonly employed by
utility bicycles. It serves to protect the cyclist from being soiled or trapped in the chain rings and tends to fully enclose the drive train. It may also contain an oil bath to keep the chain
lubricated. Modern examples are usually
moulded in
plastic. Similar devices may be found in connection with chains used on larger vehicles and machinery.