A header of general U-shaped construction having a web and depending flanges normal to the web and separated by the web, and a stud, one end of which is interfitted between the flanges perpendicular to the web. The improvement comprising vertical slots formed in the flanges through which screws are passed uniting the header to the stud whereby the stud may move vertically with respect to the stud in response to environmental forces but not horizontally.

 
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> Optical energy switching device and method

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