Katana, as you know, come in many different shapes, lengths and styles and the most immediately obvious facet of this configuration is the shape of the blade, or the sugata. One sugata that you may be aware of is called 'Shobu Zukuri'. Like a few other less known sugata, Shobu Zukuri is usually found in tanto and wakizashi forms more often than katana, and has evolved from styles normally used in naginata and nagamaki. The first shobu katana were made round the 14th century and are reputed to have been a response to the tough leather armour worn by invading mongol forces although how accurate opinion that actually is, is debatable.
Now, to many people including the factories that produce cheap blades in this style, Shobu katana are simply the more common Shinogi zukuri but without the bother of having to counter polish the kissaki. This is a horrible way to look at this style however, and the real definitive way of telling a true shobu is both more complicated in its method, but easy once you lay your eyes on one.
As well as the long, slender continuous curvature from the ha-machi all the way to the kissaki, Shobu Zukuri is typified by a high shinogi. This means that the ridgeline that runs down the blade is further toward the back than in other sugata. Sometimes the shinogi will run all the way to the very point of the blade but just as often it will stop short. If this is the case, it usually wanders slightly toward the kissaki making the distance between the shinogi shorter as it nears the tip. Both kissaki types lend an overal leaf like appearance to the blade. The shinogi-ji, the surface directly after the shinogi is tapered, or relieved quite strongly toward the back of the blade, or the mune, giving the blade a more diamond like cross section.
A modern production of a Shobu Zukuri Katana.
Given this description, It should be of no surprise that when you examine the name, you will find that 'Shobu' means Iris and 'Zukuri' in this context refers to the method of construction. So basically it means, made like an iris leaf.
Because of this slender appearance, katana in this style need to be carefully mounted in order to properly compliment the blade. Of course this is true of all katana, but because of the long elegant lines that create the curve of the entire sword, this sugata needs special consideration to be properly and elegantly dressed. This means that choice of koshirae as well as the shape of the tsuka are going to impact heavily on the feeling that you get from a shobu once it is fully furnished. Modern shobu however tend to be more 'heavily set' than their historical counterparts but makes choice of koshirae no less important. I can only guess that this results from a mix of consumer demand, the more acute edge angle and the metal lost with the relief of the shinogi-ji. But as I say, this is merely conjecture.
Image showing how the shinogi in this particular example, drifts more toward the tip of the sword.
Sometimes, it will actually meet up with the point but in this case, stops just short of it.
Now quickly concerning the use of a shobu; It is said that because of the length of the taper on the tip of the sword as well as the lack of yokote, noto becomes significantly more difficult, especially for schools that teach techniques that require the iaidoka to feel for the yokote with their fingers. Also, with the length of the tip not clearly defined and the ha's exit angle far less obtuse, it is easier to misjudge when the sword is about the leave the koiguchi and have it bite into or through the saya as it's being drawn. For this reason, these swords are not readily reccomended to practioners of JSA such as Iaido with its focus including nukitsuke and noto. This is less of a problem for people simply wanting to practice tameshigiri, or 'lop things up in the garden' however where the only thing that needs to be considered is that the tip of the sword tends to be more delicate.
So, in a nutshell, that's Shobu Zukuri. A oft overlooked style with a long slender blade and an edge thats designed to use every inch of the mono uchi. So very much more than Shinogi Zukuri without a counter polish don't you think?