[Stiglr]

Also said another way, the Poly Line tool is used to create its own discrete objects, not to modify other objects. And it creates flat objects, not contoured ones, so keep that in mind when determining whether to try to use it to create complex 3D objects.

As an example, I create aircraft mainly, and I will use the poly line tool to create a control panel for the cockpit, if I can find a picture of the panel photographed or drawn from a straight-on angle. I would NOT use it for an irregular object like a moulding or a switch with a specific shape. For such objects I'd use a modified primitive (box, circle, sphere, rectangle, disc, etc.) and then use the Knife tool and adding and positioning vertices to "isolate" areas I need to modify further. For example, I'd use those kinds of techniques to "cut" landing gear panels and wells out of the wings, leaving the "doors" separate to display on the landing gear when it's deployed.