This isn't a jig or fixture but rather a tip...
When I do my glue-ups for cutting boards I leave a 'stick' or two a bit long on either end to prevent snipe in not only the planer but also the drum sander. This has the same effect as feeding a sacrificial board before and after your target board for surfacing. I don't always get snipe on my DW735 planer but it's often enough that doing this eliminates the snipe. The little board that's protruding may get some snipe but the target board doesn't. Hope this works for you like it does for me -
David
When I do my glue-ups for cutting boards I leave a 'stick' or two a bit long on either end to prevent snipe in not only the planer but also the drum sander. This has the same effect as feeding a sacrificial board before and after your target board for surfacing. I don't always get snipe on my DW735 planer but it's often enough that doing this eliminates the snipe. The little board that's protruding may get some snipe but the target board doesn't. Hope this works for you like it does for me -

David