A solid line between nodes represents a simple Lagging Link.

The only data required for this element type is the travel time 'lag' (in minutes) for the peak flow to travel the length of this reach.  This type of link does not have any storage and does not attenuate discharges between nodes.  Consequently the total discharge at downstream nodes represents cumulation of the instantaneous discharges only taking the user defined 'lag' into account.