As long as USB sticks have a serial number they can be uniquely identified and mapped to a specific location.

Usually the sticks provide an "sda" and one or several "sdaX" devices.

To map only the "sdaX" to a unique identifier, I use the following script:

> cat /etc/udev/scripts/check_block_device.sh
#! /bin/bash
#

## Check that the devpath contains "block" for block device
## and verify that the kernel would give the device a number
## higher than 0 (like sda1)
if [ "x${DEVPATH/\/block\/*/yes}" = "xyes" -a ${1} -ge 1 ]; then
    exit 0
fi

exit 1

Now I can set a specific rules in the rules.d directory:

cat /etc/udev/rules.d/20-usb-sticks.rules
# /etc/udev/udev.rules:  device naming rules for udev
#
# USB stick rules for Gunnar Wrobel

SYSFS{serial}="1194551889523", PROGRAM="/etc/udev/scripts/check_block_device.sh %n", NAME="sticks/medion0", SYMLINK="sda%n", OWNER="root", GROUP="users", MODE="660"

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