How do I use custom.sh for a global user profile in rhel 6?

Issue

• The /etc/profile has the following verbiage:

  # It's NOT good idea to change this file unless you know what you
  # are doing. Much better way is to create custom.sh shell script in
  # /etc/profile.d/ to make custom changes to environment. This will
  # prevent need for merging in future updates.