Closed screw ...does not mean a set screw or double set screw which I like the best.
You feed the wire up through a center hole and have some wire past the end. The you screw down the banana end plug. If you get too much wire, you cannot screw down. If you get too little, the plug is not really physically secure and can pull loose.
Again I like set screw tightening the best and double set screw is even better.
These cost more from Unique Products Online, 6 pair for $42.
http://www.uniqueproductsonline.com/lobapl12pa6p.html They have 2 set screw and form a very tigth secure connection.