About Defining and Closing Gaps
Gaps are open spaces between two or more surfaces of a quilt. They consist of pairs of one-sided boundaries internal to the quilt. Each boundary is made up of one or more one-sided edges. One-sided edge is an edge that belongs to only a single surface and is displayed in pink in the graphics window. Each boundary of a gap may have a different number of one-sided edges. You can quickly and easily define or identify gaps by using the Define Gaps tool or the Search Tool.
If you use the Define Gaps tool, you must manually select the one-sided edges of the surface in the graphics window for Side 1 and Side 2 edge collectors.
If you use the Search Tool, you must specify the rules for the search operation by using attributes such as size and value to find the gaps. After you specify the search criteria, IDD automatically searches for the gaps in the active component node or active set of surfaces and highlights them in the graphics window.
After defining a gap, you can repair it in several ways. You can first add the gap to the wireframe and then click > 
Repair. However, the surfaces between which you defined the gap must belong to the same component node. If Repair fails to close a gap, you can select the black wireframe piece or pieces and click > 
Close.
Repair. However, the surfaces between which you defined the gap must belong to the same component node. If Repair fails to close a gap, you can select the black wireframe piece or pieces and click > Close.Alternatively, after defining or searching for the gaps, you can click > Close without adding the gaps to the wireframes. If you use > Close without adding the defined gaps to the wireframes, you can close gaps between any surfaces, even gaps that do not belong to the same base nodes. > Close adds the gaps to the wireframes and converts the wireframes to satisfied wireframes. However, you cannot define gaps between surfaces that belong to the merge nodes.
Close without adding the gaps to the wireframes. If you use > Close without adding the defined gaps to the wireframes, you can close gaps between any surfaces, even gaps that do not belong to the same base nodes. > Close adds the gaps to the wireframes and converts the wireframes to satisfied wireframes. However, you cannot define gaps between surfaces that belong to the merge nodes.