Abstract: A pair of bracket assemblies for mounting on the handlebars of a bicycle to enable use of a bicycle lock as an auxiliary handlebar. The bicycle lock includes a U-shaped member with spaced parallel legs. Each of the legs is supported in a separate bracket assembly. The bracket assemblies incorporate arm rests and permit longitudinal adjustment of the legs. Various types of release and securing mechanisms are disclosed which enable adjustment and removal of the bicycle lock, including angular adjustments of the legs of the U-shaped member with respect to the handlebar.