I went off topic in another thread so I thought I'd put it here
Metal framing and engineering supports.
Flexistrut Catalogue PDF
Flexistrut home page
Unistrut Catalogue PDF
Unistrut home page
Both brands are engineering standard interchangeable
Each brand has specialties the other doesn't have.
If you have friends in the commercial/industrial construction industry you may well be able to source offcuts, job left overs/freebees.
Worth a look.