  The monopole singularity string, infinite direct line in the rest reference
frame, is considered as a rigid physical line, and behavior of its geometrical
form under the Lorentz transformations is studied. The method to test the form
of any rigid line or surface in relativistical terms is based on the use of
light signals emitted from the origin of the reference frame. Influence of the
motion of the reference frame on the form of singularity line is as follows:
(1) in general case, when the line does not go through the origin of the rest
reference frame the line in the moving reference frame becomes a hyperbola; (2)
in the special case, when the line of singularity goes through the origin of
the rest reference frame, the line in the moving reference preserves its form
only modified by the relativistical aberration effect.
