The term "lunch box" was started (I think) by Petersons mag, they said "you can install one of these lockers on your lunch break."
They are referring to lockers that replace spiders and side gears in the oe stock open carrier case and these use a "ramp loading" method of locking. All those little springs do is keep everything in place they do not provide locking force.
Ramp loading lockers use the strength of the stock carrier and cross pin for all of the load. Some sell hd cross pins.

THis type of locker can unlock mid load (as seen on vids) by slight throttle let up.

A detroit locker uses heavy springs for loading and tend to stay locked much more consistantly.

When you are new at wheeling with lockers, having a rear one first is best and having a quality one installed properly into a quality axle is the way to have fun with little chance of break down.

SD

PS if wasting money installing any locker into a dana 35 axle stop right now!!! You will be flushing that cash sooner or later.