Reverse of TIFFSPLIT

I've got lots of faxes that I used tiffsplit to break up into individual pages. Then I deleted the original multipage file. Now I want to archive these faxes but it makes more sense to archive them as multi-page tiff files. (I wish I hadn't deleted those files now!). Does anyone know how to combine a number of tiff files into one multi-page file? I'd like to try and do this from the command line if possible. TIA, Jethro