Training for close combat, especially indoors, is difficult. To make it easier and more effective, special ammunition and knives have been developed to allow troops to shoot and stab each other, without causing serious injury. This is important, because "clearing buildings" is dangerous, chaotic and hard on the nerves. Very deadly for green, inexperienced, troops.
Back during World War II, commandos developed the "kill house" concept to provide realistic experience for that sort of thing. If was soon found that this provided a decisive edge when facing troops without such training, or experience in fighting in buildings. When fighting indoors, everyone is unsure of who is where and up to what. Whoever moves the most decisively, and shoots the straightest, tends to win fast, and with little loss.
Kill houses can be used firing blanks, but that does not give the same training effect. A preferred option is using "simunition." This is special, lower velocity, ammo that will leave a welt, but not cause a serious wound if you get hit. Even commandos sometimes use simunition, but this requires special parts for their weapons and, of course, the special ammunition. Much better to use the real thing (which requires much more caution).
Sometimes, troops have to rely in the knife, and a "simunition" type of knife was developed for this as well. Called the "Shocknife", this is a polycarbonate device that looks like a knife. But it can't cut. Instead, it delivers a painful (but not harmful) electric chock when it makes contact. This quickly teaches troops, training to use knives in combat, that they have been "cut." This additional degree of realism makes the training much more effective.