The item on the top left looks like a blank that goes in a 4 jaw cutter block for a woodwork spindle moulder or moulding machine . I had several. The knives were serrated backed. If I only put 2 knives in the cutter block there would be nothing to put in the 2 spare spaces so the clamps would fall out. therefore, one would put a piece of serrated steel in the space & clamp it tight. For a 65 wide * 100 diam block it would be ( from memory) about 25mm * 65mm * 8 mm Th the ends & edge that goes into the block would be square. The edge that goes flush with the block would be slightly rounded.
Sometimes the piece would be shaped rather like the cutter form but set back a bit. This was to stop the cutter digging into the wood too deep & causing an accident. On a moulding machine we did not bother but on a spindle moulder we would use them
Edited By Sam Longley 1 on 10/02/2018 22:08:08