# mkdir test
# mknod test/null c 0 26
# chmod 666 test/null
# ls -la /dev/null test/null
crw-rw-rw-  1 root  wheel    0,  26 Oct 28 13:58 /dev/null
crw-rw-rw-  1 root  wheel    0,  26 Oct 28 13:59 test/null
# echo "foo" > /dev/null
# echo "foo" > test/null
-su: test/null: Operation not supported