Geometry RESTRICT and JOIN

I'm trying to add all the "box op point" operators. The C routines are
written and working as advertised. The manuals description of the
RESTRICT and JOIN clauses of CREATE OPERATOR don't seem too clear. Are
these samples correct, or am I totally off base here?

CREATE OPERATOR << ( LEFTARG    = box, RIGHTARG   = point, PROCEDURE  = leftof, RESTRICT   = scalarltsel,     -- ??
UNSUREJOIN       = positionjoinsel  -- ?? UNCLEAR
 
);

CREATE OPERATOR &> ( LEFTARG    = box, RIGHTARG   = point, PROCEDURE  = notleft, RESTRICT   = scalargtsel,     -- ??
UNSUREJOIN       = positionjoinsel  -- ?? UNCLEAR
 
);

CREATE OPERATOR @> ( LEFTARG    = box, RIGHTARG   = point, PROCEDURE  = contains, RESTRICT   = eqsel,           -- ??
UNSUREJOIN       = contjoinsel      -- ?? UNCLEAR
 
);

...etc...