Heirloom pax is a version of the POSIX standard archive tool. It is 
from the The Heirloom Toolchest, which has code derived from original
UNIX material released as Open Source by Caldera and Sun.

Unlike some other popular pax implementations this version can create
POSIX.1-2001 pax archives. It can also can read and write zip files,
RPM packages, various tar formats (including GNU tar), and the cpio 
formats of Cray UNICOS, SGI IRIX (-K), SCO UnixWare (-c) and Tru64 
UNIX (-e).

The Heirloom Toolchest utilities use a different path structure to
avoid replacing regular Linux utilities, which may have the same name
but function slightly differently.

This SlackBuild installs pax to /usr/lib(64)/heirloom/bin, rather than
/usr/5bin (where the upstream maintainer suggests) to avoid littering
the top level of /usr. 

To use heirloom-pax, you have three choices, either call the 
utilities directly by their full paths, manually place symlinks in 
/usr/bin pointing to the appropropriate heirloom-pax version, or add
either /usr/lib(64)/heirloom/bin or /usr/lib(64)/heirloom/bin/posix2001
to your PATH variable. The PATH variable is typically set system-wide
via /etc/profile. Refer to Slackware documentation for alternative
PATH setting options.

Note: Another pax based on an old SUSE port of the Mir/OpenBSD
version is provided by SlackBuilds.org. However, despite the name
that version cannot actually produce POSIX.1-2001 pax archives, only
POSIX 1003.1 ustar archives.