sticky bit — used primarily on directories, this bit dictates that a file created in the directory can be removed only by the user who created the file. it is indicated by the character t in place of the x in the everyone category. in Red Hat Linux the sticky bit is set by default on the /tmp/ directory for exactly this reason.
source :http://www.redhat.com/docs/manuals/linux/RHL-8.0-Manual/admin-primer/ch-acctsgrps.html
