3 nodes up top, one out the bottom. What plugs into where on this module?

Say I just want to join 2 circles.

You can check out the user guide, available from the Help menu. Go to the Enhancing with Effects chapter, to the Glue module section. Here is copied from the User Guide:

The Glue module has three ports:
•Left Port (Matte): Receives the matte.
•Middle Port (Port A): Receives the element that will not be used to fill the joint.
•Right Port (Port B): Receives the element that will be used to fill the joint.

As an explanation, however, this is really not good enough to give you a full use of how to use the tool. There are two things you need to keep in mind before planning to use the glue:
1) The two parts that are being glued together need to come from the same drawing
2) There needs to be a straight cut

So you wouldn’t really use this to, say, glue two circles together. It’s more the kind of thing where you would take an arm and split it into two parts. You could do this with two circles, but you would have to put the two circles on top of each other on one drawing.

There are two ways to implement the glue:
1) Use the cutter tool to cut the drawing in half.
2) Duplicate the drawing and apply a mask.

For 1) do the following:
- Use the cutter tool, make a selection of your drawing to cut it in half
- do a cut and paste it onto a new drawing layer
- now in the Network view, connect these two drawings together in the Right and Middle ports of the Glue module
- now set up your pivot points, and you’re ready to animate!
This is by far the easier method, and is recommended above the other. The only situation in which you might want to use method 2) is if you’re working with pencil lines and you’re not getting good results when you use the cutter tool.

For 2) do the following:
- Duplicate your drawing layer
- draw a mask on a third drawing of the part that you would have cut off and pasted into a second layer if you had been doing method 1. So, for example, if you’re doing an arm, mask off the section from the elbow downwards.
- Now connect together the original drawing in the right port, the duplicate drawing in the middle port, and the mask drawing in the left port. Connect the out port of the middle drawing to the in port of the mask, as well, so that the mask will follow the transformation of this body part.
- Now you should be ready to animate.

Here is a screencap of method 2):

I hope that helps somewhat.

Toon Boom Support