What is this aluminum extrusion for?

The metals place I go to has new metal & salvage. New drops end up tossed in with salvage in some spots too.
When looking around in the aluminum, I see pieces of this odd extruded
bar scattered around the place. What is it used for?
It is always a thick round tube around 1.5-2 inches diameter, with 3 or 4 small hemispherical "teeth" placed equally around it. I've never seen any pieces more than four teeth, or less than three teeth.
See crude drawing here-
http://www.norcom2000.com/users/dcimper/assorted/inanities/metalwork/stuff01/aluminum_what_01a.png
-tiny- http://tinyurl.com/3djsq4w
????
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http://www.norcom2000.com/users/dcimper/assorted/inanities/metalwork/stuff01/aluminum_what_01a.png
Nope, but if its cheap enough you could turn it into material for rod and tube applications quick enough.
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There are three-corner modular rails, and four-corner rails, that could be developed from these sections (by milling the ribs). Any two adjacent ribs form a kind of dovetail.
Here's an optical-quality example: < http://www.optosigma.com/products/opto-mechanics/optical-rails-and-carriers/optical-rails/146-0510
I recall a rail 'system' that includes clamps and joints as well as supporting sliding apparatus. It's kinda like grown-up TinkerToys.
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