pair of suitable connected rollers 28 with one roller having an upstanding post or rod 108 which is secured to the inboard door section 52 fig3 a brace or bar 116 connects the rollers 28 together thus the two rollers 28 of each carriage means 100 move together simultaneously and in tandem and it has been found that the roller assembly tracks better than when using a single roller thereby eliminating the vibrations or the wiggling actions of the bi fold door that has previously been encountered when using a single support roller in order to enclose and to protect the carriage means 100 and rollers 28 from dust and dirt a protective cover or shield 120 fig1 is supported on the header 20 the shield 120 includes end portions 122 secured to the side surfaces of each of the upper part members 16 by fasteners or bolts 124 a suitable mounting angle 126 and clips 128 are provided to assist in the mounting of the shield 120 each bi fold door 11 is provided with a conventional direct acting shock absorber 130 the closed end of the cylinder has a lug 132 which is pivotably connected by a pin 113 to a bracket 134 carried by the upper part member 16 directly above the mounting for the corresponding actuator 30.