This is a good way of securely holding round or otherwise vise-unfriendly things without marring them.
great for spoons, tuning pegs, and other fiddly items.

also known as a bench loop, this tool uses a piece of rope to hold the workpiece in a 'V' shaped groove. The groove prevents the piece from moving around. The rope is actuated by the user's foot, something heavy, or something elastic.

This project is similar in principle to an instructable posted by Wade Tarzia. However, the kind that I learned to make is foot operated and fits in a vise.

Step 1: Block

find a stout chunk of wood that fits in a vise. an offcut section of 2x4 or larger is great. locate your nearest scrap pile and dig until you find something appropriately blocky. Soft woods work well.
I dug for a while and didn't find anything of appreciable size, so I cut a few sections of plywood from a discarded strip and glued them together. It's helpful if your block has parallel sides so it will sit snugly in a vise.

Step 2: Hole

make a through-hole in your block. I made mine about 2 cm or 3/4" diameter.

Step 3: Grooves

cut some grooves that intersect with the hole. Sitting in a groove will make it more difficult for the workpiece to shift. I used a rasp to do this. Later, when I needed to hold a bigger workpiece, I cut the grooves deeper with a saw.

Step 4: Rope

find a length of rope or cord. Tie the two ends together to make a loop. Attach part of the loop to the end of a stick, and pass the other through the hole in your block.

I used a lark's head knot to attach the loop to a stick. I cut some notches in the stick to give the knot something to bite.

Step 5: Hold Work

To hold a piece, step on the stick, or use a spring or a weight. I find stepping to be convenient because the piece is only held when I am leaning in to work on it. Here I am using a hooked knife to hollow out a piece of wood.
I also use this tool to hold down tapered tuning pegs when scooping out the head.
It works well for holding spoons when forming the dish. Here's a video showing just that.

A note on spoon carving:

the 'spoon' pictured is for demonstration of the hold-down tool. Soft woods tend to make poor functional spoons. They tend to deteriorate faster and hold on to odors better. Unseasoned or 'green' hardwood is easier to carve and yields a better final product. Fruit woods are very desirable amongst spoon carvers. They can be had easily near orchards where trees are pruned.