er necessities. By 1998, cageless collocation had become available, and CLECs that had invested heavily in cages during the post-Act big bang were left at a disadvantage to latecomers that could take advantage of cageless. But cost was not the only advantage of cageless collocation; it took up far less space, SO the central offices were less likely to run out of space. By the time the boom ended, many urban and suburban COs had indeed run out of room, although by 2001 quite a bit of space had opened up as early entrants failed. The FCC was also of assistance, creating a rule by which CLECs could request a walk-through of ostensibly full The Great Telecom Meltdown buildings, permitting them to identify vacant space that the ILEC may have thought unavailable. The FCC also allowed some limited degree of switching into collocation, provided that it did not require additional floor space. This mainly allowed incidental switching (such as emergency stand-alone mode) within a remote line terminal, and the data switching devices usually called rout- ers, which were often needed to join multiple shelves of equipment, such as DSLAMs, to interoffice transport. Many smaller ILEC buildings, especially in outlying areas, had virtually no room for collocators to begin with. Suburban and urban ones usually started out with cavernous vacant space, often used for offices or, reportedly, table tennis. This was because central office switches of the electromechanical era, such as crossbars and steppers, were far larger than the digital switches that took their place. So if the large COs were full, then one might expect that competition was robust and competitors were selling well. But it was not that way at all. Most collocation cages were nearly empty, with one or two equipment racks and maybe some spare parts. Most collocation racks were under-utilized: There was usually far more capacity present than there were customers. Many CLECs dur- ing the boom years invested heavily, using cheap capital, expecting a far larger market share