We've just had a large propane tank installed for backup generator and demand hot water. Part of this project was installing gas logs in Temco TBF36-2 and TBF42-2 fireplaces. The installer balked saying he didn't see knockouts and question whether they are gas certified. Well, the install label says they are (or were). We think we see clear knockout marks on either side of the smaller unit, rarely used. Fires in the larger unit have obscured the marks, but shouldn't be too difficult to locate. Our difficulty is that we're working without installer manuals, i.e. the units are original to the house and while we're the first owners, we've never had the manuals. Can anyone offer some help? A link to a manual? We've tried a number of places including some suggestions here, but we're stumped and need some documentation.