Side line.
1.
(a)
A line pert. or attached to the side of a thing.
(b)
Specif., a line for hobbling an animal by connecting the fore and the hind feet of the same side.
2.
(a)
A line of goods sold in addition to one's principal articles of trade; a course of business pursued aside from one's regular occupation.
(b)
A secondary road; esp., a byroad at right angles to a main road. [Canada]
© Webster 1913