Understanding hold-over and hold-under aiming
When setting up a riflescope it will be "zeroed" at a specific distance, typically the most commonly shot distance, but what if we want to shoot at a different distance without making further adjustments to our turrets?
Hold-over and Hold-under shooting is the art of using the other markers on the rifle's reticle to aim at different distances. This prevents you needing to "dial" your elevation turret to get a different zero for a different distance. It's a much faster and easier method of making the distance compensation and getting the scope ready for your next shot.
HOLD-OVER SHOOTING
DEFINITION
Hold-over shooting refers to using the markings below the center of the crosshair to shoot at targets which are further away than your zero distance. When using this type of shooting style you are aiming the middle of the crosshair above your target, hence the name "hold-over".
EXAMPLE
Below is an image of a Standard Mil-Dot reticle which has been fitted to a .22 LR subsonic rimfire rifle and "zeroed" to 75 yards. We can see that the distance written alongside the center cross is 75 yards, i.e. the "zero" distance.
On the right of each of the lower aim-points we can see a number which represents the distance that aim-point relates to.
e.g. to aim at a target 121yds away we would use the second Mil-Dot below the center cross. If we wanted to aim at a target 150yds away we would have to judge the aim-point to be somewhere between the third and fourth dots.
HOLD-UNDER SHOOTING
DEFINITION
Hold-under shooting refers to using the markings above the center of the crosshair to shoot at targets which are closer than your zero distance. When using this type of shooting style you are aiming the middle of the crosshair below your target, hence the name "hold-under".
EXAMPLE
Below is an image of a Standard Mil-Dot reticle which has been fitted to a .308 rifle and zeroed to 300 yards. We can see that the distance written alongside the center cross is 300 yards, i.e. the zero distance. 
On the right of each of the lower aim-points are the same hold-over aim-points (as in the previous example). However, now above the center cross we can see a number which represents the distance that the upper aim-points relate to.
e.g. to aim at a target 241yds away we would use the first Mil-Dot above the center cross. If we wanted to aim at a target 200yds away we would have to judge the aim-point to be somewhere between the first and second dots above center.
HAWKE'S FREE BALLISTIC SOFTWARE
Ballistics can be a complicated business at the best of times, which is why Hawke have developed easy-to-use and deadly accurate reticles with the added support of the patented X-Act Ballistic Reticle Calculator. The PC software is now also available for use on your iPhone, iPod touch, iPad and now Android devices. Just visit the App or Google Play store and search for "Hawke".