If you enable remount
http://forum.ppcgeeks.com/showthread.php?t=117999
you can then type this
su
remount rw
cat /sdcard/sprint_2.1/sab > /system/bin/sab
chmod 4755 /system/bin/sab
/system/bin/sab
remount ro
exit
exit
instead of this.
su
mount -t rfs -o remount,rw /dev/stl5 /system
cat /sdcard/sprint_2.1/sab > /system/bin/sab
chmod 4755 /system/bin/sab
/system/bin/sab
mount -t rfs -o remount,ro /dev/stl5 /system
exit
exit
just saves a little typing.