You can attach assemblies in mechanisms or mechanisms together in the scene by using attachments.

Attachment points define the location on the part where it will be joined to another body.

You can define multiple attachment points in a single assembly, but you cannot attach two components together if they belong to the same assembly.

Attachment points are attached at the Assembly level but are contained on the part in the assembly.

Defining Attachment Points

Attachment points are defined on the assembly level to allow attachments of two or more assemblies or mechanisms.

For each assembly that will participate in the attachment, follow this procedure to define where the objects will be connected:

Open the .vxassembly file containing the assembly on which the attachment point will be defined.
Right-click the part(s) you want to add the attachment point to in the Explorer panel and select Insert Attachment Point from the context menu.

You can also select more than one part and select Insert Attachment Point, and an attachment point will be associated with each part.

An attachment point appears on each selected part in the 3D View and in the Explorer panel.
In the Explorer panel, select the attachment point. You can rename the attachment points in the Properties panel.
From the Transform toolbar, select the Move or Rotate tool.
Move or rotate the attachment point to the desired attachment location on the assembly.

Once the attachment points have been defined on each assembly, you need to attach the attachment points between the two assemblies or mechanisms.

Attaching Objects Together

You can attach parts or assemblies together inside a mechanism, or attach two mechanisms together inside a scene.

Open the .vxassembly, .vxmechanism , or .vxscene file containing the components to be attached.
Select the two attachment points.
Right-click and select Create Attachment from the context menu.
By default, the two attachment points remain relative to each other represented by a line connecting the two points. (This remains true as long as the Attach Part checkbox is selected in the attachment's Properties panel.) A dotted line between attachment points represents an attachment that has been detached. To snap the two attachment points together, in the Properties panel for the attachment, click the Snap checkbox. The two attachment points now share the same position, with Attachment Point 2 moving to Attachment Point 1.
You can also attach/detach attachment points using the Attachments container, displayed above, in the Explorer panel. Click the attachment to modify; then in the Properties panel adjust the parameters. You can also right-click the attachment in the Explorer panel and toggle the Attach Part box.