Highland Park square rail saws were manufacturered between 1961/62 through the mid 1970s. They featured blade arbor bearings inside the saw tank located under a aluminum arbor cover and square carriage way rails that are set on their edge. Units manufacturered in 1961 featured square rails but did not have roller bearings on the carriage. Units manufactured from 1962 through the mid 1970s featured 12 roller bearings on the carriage - 8 on the top mounted on roller blocks and 4 on the bottom mounted on the carraige retainers.
There were oddball ones done in 1961 that featured square carriage rails but no roller bearings up top and 4 bearings mounted below with a spring-loaded retainer. These did not work all that well and tended to wear out as the aluminum carriage slid directly on the carriage rails. Unfortunately these cannot be upgraded to roller bearings as there is not enough material to machine for the roller blocks however a complete brand-new drop in replacement carriage is very reasonably priced.