There isn't any real documentation on what the fixit disk is
used for anywhere on the FreeBSD site.

Fix: 

The attached patch ands a FAQ entry that serves mostly to list
the reasons one would want to use the Fixit disk, and the other
sources of information that one might find useful when working with
the disk. I'm not sure this is the right place to put the information,
but I couldn't see any better place.

4450a4451,4519
> 
>       <qandaentry>
>         <question id="broken-root">
> 	  <para>My root file system doesn't mount. What do I do now?</para>
> 	</question>
> 
> 	<answer>
>           <para>The fixit disk is used when your systems root file
>           system cannot be mounted read-only at boot time. The sole
>           purpose of the disk is to repair the root file system so you
>           can mount it, and continue the process of bringing up the
>           system from that point.</para>
> 
>           <para>The fixit CDROM has most of the functionality of a
>           complete FreeBSD install. It does not have
>           <filename>/stand</filename>, but <filename>/bin</filename>,
>           <filename>/sbin</filename>, <filename>/usr/bin</filename>
>           and <filename>/usr/sbin</filename> are all there. You
>           should be able to boot this CDROM and go directly to the
>           fixit mode.</para>
> 
>           <para>The fixit floppy has much less functionality. All the
>           tools on it are in <filename>/stand</filename>. In
>           particular, it does not have &man.fsck.8; or &man.newfs.8;,
>           but it does have &man.tar.1; and &man.restore.8;. The fixit
>           floppy is not bootable. You must boot the install floppy,
>           then insert the fixit floppy when so directed.</para>
> 
>           <para>There are three things that can cause your root file
>           system to fail to mount. Each of these has a different
>           solution.</para>
> 
>           <para>First, if your system has slices on the disk holding
>           the root file system, the slice table may be broken. The
>           tool for editing the slice table is &man.fdisk.8;. The
>           format of the data is documented in
>           <filename>/usr/include/sys/disklabel.h</filename>.</para>
> 
>           <para>Second, the disk label may be broken. The tool for
>           editing disk labels is &man.disklabel.8;. The format of the
>           data is documented in
>           <filename>/usr/include/sys/disklabel.h</filename>.</para>
> 
>           <para>Finally, the file system proper may be so badly broken
>           that it can't be mounted. The tool for fixing this is
>           &man.fsck.8;. The format is documented in
>           <filename>/usr/include/ufs/ffs/fs.h</filename>,
>           <filename>/usr/include/ufs/ufs/dinode.h</filename>, and
>           <filename>/usr/include/ufs/ufs/dir.h</filename>.  Of
>           particular interest is the alternate superblock at block 32,
>           so that <command>fsck -b 32
>           <replaceable>disk</replaceable></command> will repair a broken
>           primary superblock. Note that &man.fsck.8; is
>           <emphasis>not</emphasis> on the fixit floppy.</para>
> 
>           <para>Other useful commands are &man.ed.1; and whatever you
>           use to restore from backups. Ed can be used to repair broken
>           configuration files, or to change them to deal with
>           nonfunctional hardware. If you are using a standard system
>           tool for backing up your system, then the ability to restore
>           backups is probably on the fixit disk.</para>
> 
>           <para>It is advisable to use &man.fdisk.8; - if appropriate -
>           to get a copy of your slice tables, and &man.disklabel.8; to get a
>           copy of your disk labels, and save them somewhere
>           safe. Printed copies for the disk your root file system is
>           on should be stored with the backup of the root file system.</para>
> 	</answer>
>       </qandaentry>
How-To-Repeat: 	Try finding that documentation.