Use this procedure to merge contiguous closed polylines, circles, hatches, AEC polygons, mass element extrusions, spaces, or blocks into a single closed-boundary object or linework entity.
All selected linework and/or objects are merged into a single entity of the type you selected first. That is, if you select an AEC polygon in Step 1 and a space object in Step 3, the resulting entity is an AEC polygon.
Merging a region with a block