Any welding options when exporting 3DS mesh?

[BigMarv]

Hi there

I'm having problems opening 3DS files in Metasequoia and a Paper modelling program called Pepakura.

I went back to basics and exported a test 3DS mesh containing a single box primitive, but when Metasequoia opens the file no object is visible, and in Pepakura it's as if the faces of the box aren't welded together.

I keep getting the advice to get 3DS to weld the sides together, but frankly I don't know what they're talking about, and they'd be first to admit that when it comes to 3DS, neither do they.

Anyone got any ideas?

Here's the sample file if anyone thinks I may be doing something wrong: http://bigmarv.50webs.com/test2.3DS

Thanks in advance

Marv