RailwayRouteOptimization/scripts/Modify/Bevel/doc/Bevel_proc_ru.html

<ol>
  <li>Enter the geometry of the bevel in the options tool bar. 'Distance 1' is
  the distance the bevel line will have from the (imaginary) intersection of
  the two edges (10 in the example shown). 'Distance 2' is the same distance
  for the second edge (20 in the example shown).</li>
  <li>Check 'Trim' if you want to trim the entities automatically. If the
  option is disabled, the two entities will remain untouched.</li>
  <li>Choose the first edge entity (a line or an arc).</li>
  <li>Choose the second entity.</li>
</ol>