Look into jailkit. The basic steps are (taken from my notes the last time I set one up):
tar xaf jailkit-2.17.tar.gz
cp extra/jailkit /etc/init.d/jailkit
chmod a+x /etc/init.d/jailkit
chkconfig jailkit on
jk_init -j /home/jail jk_lsh
jk_init -j /home/jail ssh
jk_init -j /home/jail basicshell
groupadd -g 1002 jailed_user
useradd -m -g 1002 -u 1002 jailed_user
jk_jailuser -j /home/jail/ jailed_user
Where "/home/jail" is the location of the jail on my system, and "jailed_user" is the new user that's going to be in the jail. I used UID/GID of 1002 here, but you could use whatever you like.
This will give them access to a basic shell, and if you "mount --bind" the design directory into their home directory in the jail they should have access to those files as well. You may need to "jk_init -j" some more utilities if they need them, such as text editors, etc.
Most of these steps are taken verbatim from their documentation.