Piles are used to transfer surface loads to a competent soil or rock at depth when the surface layer is not adequate or is not economically feasible to use.This load transfer may be by vertical distribution of the load along the pile shaft (skin friction) or a direct application of load to a lower stratum through the pile point (end-bearing). Piles can also serve to carry lateral, uplift and overturning loads. Driven piles are typically delivered to construction sites prefabricated and consist of either reinforced, pre- or post-tensioned concrete, timber, open- or closed-ended steel pipe or H-beams. Diesel hammers are the most common driving mechanism used to drive piles although other driving methods are seldom used. A primary drawback to driving piles is the large noise and vibration associated with this form of deep foundation construction. Driven piles are typically of small diameter and are often grouped into clusters or rows. The pile groups are then tied together using pile caps or grade beams that carry the column and wall loads. An indicator pile program can be conducted at the onset of construction using a pile driving analyzer, to help correlate driving energies and capacities, and optimize design.