Aluminum track for hanging curtains, balancers, hand tools, electrical cables etc. The advantage of the aluminum rail is that it has a longer distance between the attachments. Used when suspended from high ceilings.
Clarifying illustration:
G: 112170105 Aluminum runner
K: 112170402 End cap for aluminum runner
L: 112170303 Aluminum splice piece
M: 81071201 End cap for runner
N: 920163 Runner 1-axle
O: 920167 Runner 2-axle
P: 81071003 S-hook
Q: 81071706 Pull cord with ball
R: 81071805 Suspension strap