You have in your possession a walnut press. You lift the handle, screw the end either in or out depending on the size of the walnut, insert the walnut and bring down the handle, cracking the walnut enough for you to peel off the hull. You make sure the walnuts are segregated into like size groups so you don't have to adjust the end all the time. If you're good enough, you'll get the two halves of the meat out unbroken.
I have used one for years and just recently finished eight, 5 gal. buckets of walnuts from our tree. Tedious though, just like processing brass.