.. function:: fixZ(z, *constrValues, '-tol', tol=1e-10)
Create homogeneous SP constriants.
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``z`` |float| z-coordinate of nodes to be constrained
``constrValues`` |listi| a list of constraint values (0 or 1),
must be preceded with ``*``.
* ``0`` free
* ``1`` fixed
``tol`` |float| user-defined tolerance (optional)
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