[FirstYorkie]

Yeah, I'd probably keep it shut until both of them are comfortable with it, too. I bet Haggis will follow Starsky's lead before too long.

To speed up the process, you could try this. First, tape open the flap. Start rewarding Haggis for going any where near it (even just in the same room, if need be). Good dog! You are so brave! Here's your treat! Gradually work him up to going all the way up to it for his praise and treat. Then through it. That might take a REALLY good treat - like a small bit of cheese or leftover meat. Repeat many times with the flap taped open. Then try it with a towel for the flap (as described above). Then progress to the real flap.

Good luck!