Use the Fuse tool to connect discrete topology surfaces/solids/parts. The Fuse tool can be utilized to connect close proximity inputs by defining a threshold.
Create/modify solids by dragging selected surfaces.
If multiple surfaces are selected, the Drag tool will offset each of the surfaces
along the normal direction. You can retain the shared edges, or modify them. If a
floating surface is selected, a solid is formed on the offset.
From the Geometry ribbon, Drag/Spin tool group, click the Drag
tool.
Left-click to select the surface(s) to drag.
Optional: Select one or both of the offset options in the microdialog.