There are several online shops that sells protectors for your DE razor these days, mostly made from plastic. You can even download a file to 3d-print your own, if you’re so inclined and have a 3D-printer handy. But did you know that the concept is about as old as the Gillette safety razor itself?

The protector for the cutting edge or edges of the blade comprises shield sides bent over to form pockets for enclosing the cutting edges of the blade when the shield is inserted over the back plate, the blade and the guard. This shield is transversely curved as shown and is of such shape that when the arts are drawn into position for use of the shield may be readily slid into and out of its protective position.

In short, the protector would also serve to keep the head and blade assembly together when the handle was unscrewed completely, thus allowing the blade to be kept in the razor even when the razor was packed away in a travel kit or drawer.

Another one of Mr Thompson’s patents assigned to Gillette Co, this one dates from 1929 and highlights Gillette’s attempts to make a better blade than the original three hole design – a search that didn’t end until Gillette acquired the Probak Corp (and their parent company; AutoStrop Co) and started using the slotted Probak blade we know and love today.
This 1929 patent is trying to address one of the key issues with a safety razor with replaceable blades; the accurate and repeatable positioning of a mass produced, loose tolerance blade in the razor. To quote Mr Thompson in his patent text:

In the use of razors of this type satisfactory operation depends in a large measure upon the accurate positioning of the blade with respect to the cap and guard and the positioning of the cap and guard with respect to each other. A slight inaccuracy in relation of these parts will result in an uneven edge exposure of the blade at different points in its length, or may produce an excessive edge exposure which renders the razor dangerous.

King Gillette originally solved the problem with having three holes that had to line up with three studs. Today we have a stilted blade that can line up with a raised bar, or studs, or a combination. Both designs makes the manufacture of the razor head somewhat complex, since multiple studs or a raised portion has to be machined into the top cap or base plate. A blade with just one hole on the other hand… then you could get ways with just the threaded stud that holds the handle, as shown in the drawing.

A quick sidebar; the razor shown in the drawing looks very much like the Gillette Single Ring as manufactured in the twenties.
So how did Mr Thompson intend for this blade design to easily and accurately align with the cap and guard? By bending the ends of the blade into flanges that would naturally align with the short sides of the base and cap… one turned up, the other turned down. This would – in fact – serve to align the blade, but at the cost of not being able to easily wrap them in paper and pack them flat. Looking at the drawings, the blade was modified from the three hole blade with the rounded sides, which would simplify the production.
It’s hard for me to judge how serious this design was meant to be all the time Gillette was experimenting with a slotted blade at the same time. Possible this was a case of patenting something just to stop the competition from making blades this way, literary throwing stuff at the patent office to see what stuck.
In hindsight there is a better, simpler, and cheaper way to make a razor with just one threaded stud… but I think that in order to see it you needed to be familiar with the modern DE blade; the one developed from the Probak blade with notched corners. It’s clearly shown in the cheap and cheerful razor I bought from Flying Tiger Copenhagen close to two years ago; raised corners on the cap that engage the notched corners, as the photos below shows.

This patent shows an interesting attempt at moving away from the three hole blade before the patents expired, even if the shape would have made packaging more complicated. In the end though I do believe the modern slotted blade is a better solution though, especially as it’s backwards compatible with the older razors originally manufactured for the three hole blade.