Join lines with coinciding ends into a new, single line object. Redistribute any data attribute fields according to transfer rules .
In the example shown above, suppose A1, A2, A3, B1 and B2 are all separate line objects. Suppose further that the ends of the lines are exactly coincident and do not have gaps between them as shown in the illustration Running the Join Lines transform on the selection contain these five line objects will create two new line objects.
One new line object will be made up of A1 + B1 + A2. The other new line object will be made up of A3 + B2.
Given an arbitrary set of lines it can be remarkably difficult to join "coincident" lines. After all, consider that lines can be multi-branched objects like areas. In the case of multi-branched lines what appear to be two different line objects can be the same object. For example, in the illustration above a topologically complex (and weird) drawing could have B1 and B2 both be branches of the same line object and A1, A2 and A3 also be three different branches of the same line object.
Given a set of lines the Join Lines transform creates a network with a link for each branch of each line and then composes another set of lines that collapse chains within the network. Note that chains could consist of parts of different objects). This algorithmic approach combining graph theory and computational geometry provides a flexible, reliable transform operator that can deal with arbitrarily complex topology.
Dissolve - The Dissolve tool can join lines by data attribute. It uses the Join Lines algorithm to join lines together that have the given data attribute.