About Aligning the Mesh Elements
In the Freestyle Modeling environment, you can associate or align the mesh elements on the control mesh with the external geometric references. You can also break the association. The commands supported for these operations are as follows:
• Align
• Unlink
You can use the following as reference to align mesh elements and to create Freestyle geometry:
• Datum planes
• Planar surfaces
• Surfaces or quilts
• An edge or a chain of edges
• A curve or a chain of curves
You can select the following options from the 
Align overflow menu:
Align overflow menu:• 
Align—Aligns the mesh edges to an external geometric reference. When aligned, the vertices of the aligned control mesh can move only along the reference edge or the curve.
Align—Aligns the mesh edges to an external geometric reference. When aligned, the vertices of the aligned control mesh can move only along the reference edge or the curve.• Align Normal—Aligns the mesh edge to the external geometry such that the aligned surface is normal to the external reference geometry. The external curves and edges used as reference must be planar and nonlinear.
Align Normal—Aligns the mesh edge to the external geometry such that the aligned surface is normal to the external reference geometry. The external curves and edges used as reference must be planar and nonlinear.• 
Align Tangent—Aligns the one-sided edge or a loop of edges to the external geometry such that the aligned surface is formed tangent to the external surface. The external geometry is a curve on surface or two-sided edge. If you use a two-sided edge as reference, both surfaces are highlighted. You can select a surface as the reference for the tangent alignment.
Align Tangent—Aligns the one-sided edge or a loop of edges to the external geometry such that the aligned surface is formed tangent to the external surface. The external geometry is a curve on surface or two-sided edge. If you use a two-sided edge as reference, both surfaces are highlighted. You can select a surface as the reference for the tangent alignment.• 
Align Curvature—
Align Curvature—Aligns the one-sided edge or a loop of edges to the external geometric reference such that the Freestyle surface is formed along the external curvature.
By default, associativity is maintained between the resultant Freestyle geometry and its references. You can click 
Unlink to remove the connections, and break the surface alignment. In case of multilevel subdivision mode, you cannot move the vertices on the aligned edges.
Unlink to remove the connections, and break the surface alignment. In case of multilevel subdivision mode, you cannot move the vertices on the aligned edges.The aligned shapes have aligned regions listed under them. Click an arrow next to a shape to expand the shape. The expanded aligned shape shows all the align regions. You can change the alignment type or unlink the shapes by right-clicking the aligned region and selecting the appropriate option.