How do you merge nodes?


I am attempting to correctly set up a fluid structure interaction simulation that implements an ALE group.
I have created a 'work piece' that is modeled as a SOLID ALE Material. This work piece is allowed to deform/flow into a surrounding 'void space' which is also modeled as a SOLID ALE Material. The void space is a component with a space exactly matching the work piece's dimensions cut out of it, such that the work piece fits perfectly within the void space. In other words the void space perfectly surrounds the work piece. Both of these components have been 3D meshed using quad elements. And the element sizes of both of these components are exactly the same.
I have been informed that in order for these components to interact together properly the meshes of the void space and the work piece must share the same Node ID's on their common boundaries. I.E. these nodes must be merged.
How is this accomplished?
Thank you for your help!
Brad