the door can then be actuated a frontal view of the door with the lift rods 200 210 as shown in fig1 as might be expected the door being made of aluminum will tend to expand and contract with variations in temperature as will doors made of any material that has a coefficient of thermal expansion that tends to create binding on lift member depending on the dimensional relationships established and the range of temperatures to be accommodated the requirement of positional accuracy and the freedom for thermal expansion is accommodated by making one door support rod the left rod 200 here a fixed rod such that the end of the rod 200 for example as shown in fig1 is tightly clamped to the fixed hole configuration in the slit valve door the machine screw 72 engaging the end of the rod tightly clamps the end of the rod 200 to the shoulders of the narrow pass through hole 63 in the inner slit passage door 60 this tight clamping provides a good electrical path to ground from the door so that the possibility of arcing is reduced or eliminated and further sets a horizontal and vertical position of one end of the door this clamping acts as an anchor or pivot around which the other floating end of the door and its support can move fig1 shows the right hand rod floating rod 210 its rod receiving hole 68 is elongated in a sideways direction e g.