The Attach options determine how curves or surfaces are modified when attached. Select Attach - to display the Attach Options box. The followingdescribes each Attach type and shows close-up examples of each. These are the original curves. Blend modifies both elements, in order to blend the two endpoints of two curves or the edges of two surfaces to create one element.
Blend is the system default.
Fit attaches two elements by modifying the second element you select, to fit its endpoint or surface edge to the first element. The first element is not modified in any way. The higher the degree of the second element, the larger the extent of the change. If Knot Insertion is toggled ON , an additional edit point is inserted in the last span of the second element you select. This lessens the modification effect on the element that is being fit.