1. Holding the grenade in the throwing hand, thumb over the safety lever, pull the safety pin (pull force of 10–35 pounds or 45–155 newtons).

2. When the grenade is thrown (safety lever released), a spring throws off the safety lever and rotates the striker into the percussion cap.

3. When struck by the striker, it ignites and sets fire to the fuse, or powder train. The fuse burns at a controlled rate, providing a time delay (usually 4–5 seconds). When the flame of the fuse reaches the detonator or igniter, it causes action on the filler.

4. A detonator is similar to a small blasting cap. Very sensitive to heat, when the fuse burns into it, it causes the grenade to explode.

5. An igniter is a cap that burns rapidly. It sets fire to the filler causing a rapidly expanding gas which bursts the container.

6. The fragmentation grenade shown uses a detonator.

Hand grenades are usually designed to make them easy to throw. For example they weigh around 500 g (1 lb) and have a diameter of 100 mm. Due to the design of grenades left-handed people hold them upside down when thrown. The average grenade can be thrown about 25 to 35 meters by the average soldier. They use a compound of RDX, composition B or TNT as their explosive.

Classical "pineapple" grenades, such as the Mills bomb, used smokeles powder and cast-iron shells, which (in theory) would fragment along deliberately-cast weak points in the shell—although the pattern on the grenade body was actually intended to allow the user to have a firm grip on the grenade. In practice, external grooves in the grenade body turned out to have little or no effect on the size and shape of fragments formed.

Grenades have also been made to release smoke, tear gas ("CS"), and other gases, as well as illumination. Special forces often use "flash-bang" grenades to disorient people during an entry into a room, without the intent of causing lasting injury.

Some grenade designs were made to be thrown longer distances. The German "potato-masher" grenade had a long wooden handle that extended its range by fifty percent. The "potato-masher" was fired by a friction igniter in the head, which was activated by a pull string threaded through the hollow stick. Immediately before throwing the grenade, the soldier pulled a small plastic ring attached to a string attached to the friction igniter. This started the time fuse which fired the detonator after a delay. The "potato-masher" is often incorrectly thought to have had an impact fuse. It did not, but the superficially similar British stick grenade design of 1908 did have such a fuse.

Fragmentation grenades

The fragmentation grenade (commonly known as a "frag") is an antipersonnel device that is designed to damage or destroy its target with a burst of flying shrapnel. The body is made of hard plastic or steel. Flechettes, notched wire, or the case by itself provide the antipersonnel fragments. The filler may also include small metal balls to injure the target. When the word "grenade" is used without qualification and context does not suggest otherwise, it is generally assumed that a fragmentation grenade is referred to.

These grenades are usually classed as defensive grenades because the effective casualty radius is greater than the distance it can be thrown; it is assumed that they will be thrown from behind cover at attackers. The hand-sized Mills bomb with a cast iron casing is an example of a defensive grenade.