Here is the instructable that I promised to make if my goal was achieved. It is a bit difficult to make due to the fact that it is round and you are drilling on it and it is simple to use.
Step 1: Part one materials and moveing them to workplace
Gather your materials and take them to your work place. You will need a toilet paper holder (it does not matter if it is metal like mine or if it is plastic) that comes apart into two pieces with a spring in it, some plastic cutting knives that you use at bbq's and such, a drill (not shown), scissors (not shown), a drill bit big enough for the nail (not shown), a thin nail, and tape (either duct or electrical I used both in my prototype). Optional things to use are a close pin, spray paint, and hot glue. Also in this I did not make another one I just used the one I had so ignore the close pin.
Step 2: Part two gearing down your toilet paper holder
This should be very simple just pull the big end from the small end and there should be three parts a big end with a spring in it and the small end which will hold the knife.
Step 3: Part three prepareing to drill
Be very carful on this step due to the fact you can lose the small end inside the big end and that you are using a drill. Put the small end inside the big end with the hole facing out as shown in the picture. Put it in so there is only around a few centimeters out of it. I am sorry for using centimeters I am using it because it is less than an inch. Now drill your hole into it.
Step 4: Part four preparing the knife
Now take your plastic knives and cut the ends off as showed in the picture. Then take the blade ends of both of them and overlap them as shown in the second picture. Then tape or hot glue them together and tape the bottom big enough so it stays in the hole of the blade housing (small part of toilet paper holder).