trolley configuration double girder trolley superior clearance and headroom for double girder crane applications. normal headroom trolley an ideal selection for monorails and jib crane applications. hardened wheels for pa......trolley configuration double girder trolley superior clearance and headroom for double girder crane applications. normal headroom trolley an ideal selection for monorails and jib crane applications. hardened wheels for patented track applications are also available. low headroom trolley the best solution for single girder cranes its compact design provides maximum space-efficiency.