A tubular cast on employs a number of very specific steps, including slipping stitches alternately on the ribber and main bed. The edge is "rounded" and similar to a tube.

One method of creating this beautiful cast on is with a "broken toe" method. Use this method to prevent the cast on edge from flairing and ruffling.
See also Kitchener Bind Off Broken Toe Cast on

Classroom:
Ribber Basics