[Old Man Dave]

The tongue is (was) a piece of metal about 3 inches long x 2 inches wide x 3/16 ths inch thick. The thing is that you have to taper it so as to remove it from the lead once it's set. This creates the hole for the belt. Taper needs to be 2 down to 1 3/4 inch on width and 3/16 down to 1/8 on the width. There's a slot in the side of the tube mould to take the tongue. I filed the slot half into each of the halfs of the tube mould - if you see what I mean. Click on one of the mould thumbnails to enlarge it and all should become clear. If the tongue is a reasonable fit and you don't make the lead too hot it don't leak. It's a bit slow pouring, slitting the mould, cooling the lead and then removing the tongue (with a mallet) but it works. The lead shown in the picture has not been cleaned up at all except for cutting off the sprue, thats the bit where it's poured. Like I said a bit slow but you can make a belts worth in a morning. Hope that's helped. Can let you know more if you want.
Dave.