Edge Tangency
Edge Tangency controls the way the connecting splines are drawn. When the Tangency command is executed, splines from the second entity selected are re-drawn and extended so that they become tangent to corresponding splines in the first entity. The corresponding splines in the first entity will be modified slightly or remain unchanged depending on which Edge Tangency option is chosen.
Average Both
Splines in the first entity selected will be changed slightly in making the connecting splines tangent.
First Element
The splines in the first entity selected will remain fixed. Only the splines in the second entity will be changed in making the connecting splines tangent.