Do Vanishing Cabinets come in pairs or singles?

Question

After seeing this question and some of the discussion on it got me wondering if this pair of Vanishing Cabinets was common or rare...

How did Dumbledore not know that the Vanishing Cabinet was one of a pair?

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We know that Draco had to repair the cabinets after he realized there was a connection.

The other’s in Borgin and Burkes, said Malfoy, and they make a kind of passage between them. […] I was the only one who realised what it meant – even Borgin didn’t know – I was the one who realised there could be a way into Hogwarts through the Cabinets if I fixed the broken one.' - Harry Potter and the Halfblood Prince, ch. 27 ‘The Lightning-Struck Tower’

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Then from the films we have this scene Mr. Weasley's Information

You can see the appeal, should the Death Eaters come knocking, on would simply slip inside and disappear for an hour or two. Could transport you practically anywhere. Tricky contraptions though, very temperamental. - Harry Potter and the Half-Blood Prince (film)

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Dumbledore lead Draco to believe this was a very clever idea, and one that even Dumbledore did not think of:

Dumbledore’s sigh was half a groan. He closed his eyes for a moment. ‘That was clever… there is a pair, I take it?

‘Very good,’ murmured Dumbledore. ‘So the Death Eaters were able to pass from Borgin and Burkes into the school to help you… a clever plan, a very clever plan… and, as you say, right under my nose…”

However, my recollection of the story line was that Dumbledore essentially allowed Draco to carry out his plan. Dumbledore knew Snape had made an Unbreakable Vow with Draco and encouraged Snape directly help Draco. In the tower scene Dumbledore is just stalling and trying to get in Draco's head so that Snape will have have to be the one to finish the job.

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Regardless of whether Dumbledore knew the cabinets were a pair or not, do we know if Vanishing Cabinets were produced as pairs or as stand-alone items or was the identical pair we see unique?

Answer 1

Based on the exchange between Dumbledore and Malfoy, I find it rather more likely that they do not generally come in pairs. Whether or not the pair at Hogwarts and at Borgin & Burke's is unique, I cannot say, but they certainly appear to be an unusual case.

You point out in your question that Dumbledore seems surprised that there is a pair, but you are justified in doubting whether Dumbledore is simply being deceitful and stalling for time. But look at Draco's response:

"That was clever. . . . There is a pair, I take it?"

"In Borgin and Burkes,” said Malfoy, "and they make a kind of passage between them." (from Half-Blood Prince, Chapter 27)

Why would Malfoy feel the need to explain this if it were common knowledge? Malfoy, having grown up in a wealthy pureblood family, is very familiar with the workings of the wizarding world and must assume Dumbledore is as well; he would hardly feel the need to explain that one could travel between two Vanishing Cabinets, much less use such uncertain words as "kind of" to describe it, if not for the fact that Vanishing Cabinets do not generally have this feature.

Another reason why I suspect it is unusual for Vanishing Cabinets to come in pairs is that otherwise, the staff would certainly not allow the Vanishing Cabinet to remain at Hogwarts. Sure, Dumbledore and Snape might have had their own reasons for not interfering with Draco's attempts, but what had happened to Montague meant that the presence of the Cabinet in the school was common knowledge. Surely someone in the staff -- Filch, perhaps -- would have done something about it if Vanishing Cabinets tended to come in pairs.

There is, of course, an alternative explanation: disregarding the line in the movie, it could be the case that the two Vanishing Cabinets are in fact the only ones in existence. This would explain the words of Draco and Dumbledore and the actions of the staff just as well. In any case the existence of a pair of connected Vanishing Cabinets is unusual.

Answer 2

From how I understood the concept of the vanishing cabinets, I believe that the cabinets came as a pair, and were used as a means of transportation e.g. as a means to escape Deatheaters. However over time, and due to to destruction of most cabinets, they fell out of use, resulting in only single vanishing cabinets being left.

Answer 3

It would make it so much cooler if they came in singles and Draco managed to turn a bug into a feature.

The only thing is, when he's at Borgin and Burke's he asks "Can you fix it?" He doesn't say "Can you help me perfect this weird and rare connection?" or something along those lines.

To fix the cabinet would mean to make it single again, so you could vanish into nothing or a while with it again. It would break the connection Draco wanted. So that wouldn't make sense if cabinets came into songles, right?