Model SD30SOL-HOM kit fits 30 space Square D HOMELINE (NOT "QO") Panels where a 2-pole solar breaker is located on the TOP LEFT breaker position and a 2-pole gen breaker is located on the BOTTOM RIGHT breaker position with a bottom mounted main breaker.
 
This kit will work with a top mounted main breaker as well with a TOP LEFT gen breaker and a BOTTOM RIGHT solar breaker in that case.
 
The interlock functions as follows:
 
Position 1:
Gen breaker is locked out. Main and solar breakers can be turned on or off independently.
 
Position 2:
Main AND solar breakers are BOTH locked out. Gen breaker may be turned on or off.