Schlage F61 V GEO 619 house door lock - double knob, keyed outside.

It includes a sleeve a half inch long. This is put on the bolt mechanism.
Remove mounting bracket, slide on sleeve, replace bracket. Except that I
can't seem to remount the bracket with the sleeve in place. I finally gave
up and removed the sleeve, reassembled bolt with bracket and installed the
lock.

Anyone have any idea what the sleeve is for? Some security device?
Everything seems to work without it. I've locked, unlocked, etc. with and
without key multiple times.

TIA

--
"Where there's smoke there's toast!" Anon