what do you use to hold your neck solid while fret leveling?

I was trying to do a fret level and the guitar kept moving around on the table. What is a good cheap way to hold the neck solid with good support so i can level the frets without using one hand to hold the guitar steady?

When I'm not using the neck jig, I use one of these guys, usually with a slab of wood stacked underneath so it's at the right height. The body rests flat on the bench and this supports the neck.

http://www.stewmac.com/product_images/1lg/4479/Neck_Support_Caul_sm.jpg

The cork lining is sticky enough that it doesn't move around on the caul.

To keep it still, you could use some of that foamy stuff that they sell as router mats, carpet grip padding, and drawer liners. It's all the same stuff, but it's usually black when you buy it as a tool chest drawer liner.

http://www.woodpeck.com/media/main_router_mat.jpg

Couple bags of rice and a light touch.

The one neck I did a L&C on I took off the guitar and placed it on a board so it would sit level without my having to remove the tuners. Since I have a marble sanding block (fairly heavy) and I knew I wasn't going to have to do any really heavy-duty sanding, I was able to hold the neck still with my other hand and let the weight of the sanding block provide the downward force while I moved it with the other hand. Worked out pretty well.

I had noticed during the modification process (a very heavily-modified Squier Bullet Strat) that the neck with no tuners on it sits level on the back of the headstock and the back of the neck-pocket end. Thanks, Fender, for doing that for me!