The LIB command opens part libraries and let you insert drawings as a group. LIB is a means to contain very large collections of not indexed items. Before use you have to define option keywords to root directories where items are stored.
Definitions are stored in ac_cufor.cfg or bc_cufor.cfg as part of the CUFOR selection.
Syntaxis and example:
#option;description;path; veh;Vehicles;x:\data\cad_users\libraries\vehicles;
In this case, LIBVEH shows a dialogue pointing directly to x:\data\cad_users\libraries\vehicles so you don't have to browse through complex file structures every time.
After selecting your item, it is inserted a group. You may want to turn PICKSTYLE to 1 in order to select and turn PICKSTYLE to 0 if you need to edit the item.