A very good example is the quirk of a beading plane. You simple don't see beading planes without boxing. The quirk would very quickly wear away without it.
There are other places that you would see boxing used in profiles and even boxing for fences. I talk more in-depth about boxing in a post here.
I thought it would be interesting to share my approach to installing boxing via a video. The process is essentially to make strips of boxing. It is not easily described how I rough out the boxing strips but it involves a slot cutter. All the strips are roughed out over size and then individually fitted to the groove cut in the plane body. I cut this groove at the table saw.
The process is involved but when done right it can be glued in with hide glue and just tapped into place with a hammer and that is it. I do not use any clamps to secure the boxing while it drys. Even without the glue the boxing would be difficult to remove just on the friction needed to tap it into place.
This is an approach I learned while fitting mortice and tenon joints in chairmaking. If you could push the tenon in about half way and it stops without using more force (hammer) then you have a perfect fit that glue only adds a bit more confidence in the joint withstanding stresses in use. The hide glue also acts as a lubricant to make tight joints slide together, unlike a PVA which would bind and lock up in this situation.
You'll notice that the video ends suddenly since my memory ran out right at the end but you get the gist of the process from this video. :)
I hope you enjoy!