Compare this function with the Modify>Break>SmartSingle function. To understand the use of these two functions (SmartBoth and SmartSingle), it is helpful to compare them with Modify>Break>Both.  With Modify>Break>Both, break is accomplished by selecting explicitly the two desired entities involved in the break. But with the smart functions, it is only necessary to select one entity. KeyCreator then automatically selects the second, intersecting, entity nearest to where you clicked on the first entity. So the location where you click on the first entity is crucial in determining which second entity KeyCreator selects automatically for the break operation.

SmartBoth does what SmartSingle does (break the selected entity to the intersection of its closest neighbor) and additionally it breaks the closest entity to that same intersection position as well. Note this special case: if both the selected entity and its closest neighbor are closed entities, the function defaults to a break single of the selected (closed) entity, looking for and breaking against two distinct points of intersection. It ignores breaking the closest entity.   

Note that the SmartBoth function does not support selection of solid entities. (The SmartSingle function can break a solid that intersects wireframe geometry, not a solid that intersects another solid.)

Using the Function

1. Click Modify>Break>SmartBoth.

2. Select the entity to break or extend on the side you want to keep and on the side of the closest second entity you want to break. The function breaks or extends the first entity with respect to its intersection with the second, and it breaks or extends the second entity with respect to the common intersection. If the selected entity is closed, the function first tries to break against a single closed entity. Failing that the function breaks it (Double) with respect to the two closest entities. This is followed by a break of the closest entity to the selected entity. If both the selected entity and the closest entity are closed, the function breaks only the selected entity with respect to the two closest entities, and ignores breaking the second entity. If there is no intersection found for the selected entity, the function fails. If it succeeds in breaking the first entity and fails for the second entity, an error message appears.    

Example Modify Break Smart Both: