Lock em tight with this Bed and Bath locking set of door knobs made by Dexter by Schlage.  It has a Lifetime mechanical warranty, and 5 year warranty on the finish.  This is new, in the original packaging and unopened, so the warranties may still apply.  Its rated ANSI Grade 3 and comes with detailed instructions.  The adjustable latch fits 2 3/8" - 2/34" backsets, and it fits 1 3/8" to 1 3/4" thick doors.  It has an easy-open privacy function to prevent lock-in situations (ideal if there are children in the home).