Hydraulic hand pumps use human power as the input, outputting hydraulic energy. While many hydraulic pumps are operated by other means of power, such as electricity, compressed air or even hydrostatic flow, a hydraulic hand pump relies on human force to effect the action desired. They are ideal for use where conventional power inputs are unsuitable or unavailable, and are also well suited to portable applications. Hydraulic hand pumps are commonly used to load and test machinery components, especially when a fine degree of tuning is desired. They are also used in materials handling machinery for raising and lowering heavy objects, which also require a fine degree of control over the movement of the items that can only be achieved by human intervention in the process. There are two types available; single-acting hand pumps (HPMU) or double-acting hand pumps (HPMR). HPMUs exert force on the down stroke only, whereas HPMRs exert force on both the down and up stroke. For the sake of speed an HPMR is the better choice, but not everyone considers these to be the better option, and they are more complicated to maintain and repair if things go wrong. HPMUs are much simpler in construction, but it takes twice as long to generate the same amount of movement with these than with an HPMR. All hydraulic hand pumps manufactured by Hydraproducts are available in 12, 25 or 45 cc sizes and can be flange-mounted directly to the tanks with a capacity of up to 10 litres. The direction of the HMPRs is controlled by a lever, allowing both forward and backward powered motion; a relief valve is available if this is preferable to dual-directional power for a specific application. HPMUs act in a single direction only, with the cylinder returned to the start position by way of a relief valve. The main benefit to a workforce is the lower level of exertion required by a person to affect the same amount of movement when using a double-acting hydraulic hand pump, compared to a single-acting hydraulic hand pump; the effort required must be reasonable and sustainable. This is especially important in materials handling applications, as the effect of muscular fatigue on the concentration of the operator needs to be considered for the sake of health and safety; as well as the potential for wastage due to human error.