If a projector is aligned non-perpendicularly to a screen "Keystoning" can occur which means the image looks trapezoidal rather than square.
The NEC MC372X, like most classroom projectors in its class, does not offer horizontal/vertical lens shift. To properly fit the image to a screen you will need to physically move the unit left/right and up/down. However sometimes you can only move the projector so far. For example, in my media room, I could only move the units a few feet before I had to resort to keystone correction to try to properly fit the image on my screen. We recommend you only use digital keystone correction as a last resort because it reduces overall resolution of the image but sometimes it is necessary.
The MC372X offers both vertical and horizontal adjustment while many units in its price point only offered vertical adjustment. Since I usually place projectors I am reviewing on a fixed shelf in the back of the room, this could result in some noticeable horizonal keystoning in images displayed on my permanently mounted drop-down screen. Without lens shift, this distortion could only be corrected via keystone correction tools.
The MC372X not only offers traditional vertical and horizontal keystone correction, it also offers PINCUSHION and CORNERSTONE adjustments. The CORNERSTONE adjustment allows for precise adjustment of the 4 corners of the image. You can simply drag the corner to where it needs to be. The PINCUSHION adjust can be utilize if the image has some visible bowing at top/bottom or left/right.
To be fair the person who is buying one of these projectors is probably just going to place the unit on a table and move it around until the image looks halfway decent on a wall or portable screen. Regardless, the MC372X’s powerful set of keystone correction tools could be very useful in many situations.