If Job is your polymorphic relationship then they should be
class Job extends Model
{
// think of a better general name for the polymorphic name.
public function jobable()
{
return $this->morphTo('jobable');
}
}
class InstallationJob extends Model
{
public function jobs()
{
return $this->morphMany(Job::class, 'jobable');
}
}
class Project extends Model
{
public function jobs()
{
return $this->morphMany(Job::class, 'jobable');
}
}