These piles include vibrating, impact driving, hydraulic pushing, jetting, and trenching. The type of sheet piling often governs the method of installation. Contract specifications at times may prohibit the installation of sheet piling until the contractors methods and equipment are approved. The types of pile driving hammers used for the installation of steel sheet piles include vibratory pile hammers, diesel, air stream, hydraulic impact pile hammers, hydraulic sheet pile “pushing rigs” a high pressure jet w/jet pump or a simple drop hammer. Vibratory pile hammers are widely used because they usually can drive sheet piles faster and do not damage the top of the pile and can easily extract piling when necessary. Superior Foundations will use guide structure or templates to ensure that piles are driven correctly aligned. Templates can be also used to obtain the proper plumbness of the sheet pile wall.