For each line you place a new collider at the position and make its size of the length and a define height.
Draw your line
direction = end - start;
length = direction.magnitude;
BoxCollider bc = line.AddComponent<BoxCollider>();
Vector3 s = bd.size;
s.x = length;
bc.size = size;
this above is surely not working as it is, you need to make it proper but this should get you on the path of success.