Use common sketch tools for manual placement of rebar shapes within a valid host.
Video: Detail with Planar Rebar
Rebar sketches will map to an existing shape when they share the following attributes:
If the sketch does not match an existing shape, a new shape will be created in the Rebar Shape browser and Rebar Shape type drop-down in the Options Bar.
Sketching a rebar shape
Adding rebar hooks to the sketched shape