[CentOS] building rpms

Hello,
    I've got a centos 4.4 box and i'd like to make some rpms for it. My 
first task is to recompile an srpm removing some options to customize it. I 
tried rpmbuild, which worked on a fedora install, but that command wasn't 
available. What rpm do i have to install to make rpms? I've got rpmdb, rpm, 
and rpm-libs already installed. I thought the missing one was rpm-utils, but 
no go.
Thanks.
Dave.