If you are placing ring bolts and U-bolts then you must use an injection glue system. Most bolt manufacturers produce high quality glue which is deposited using a brand specific caulking gun. The two parts of the glue are mixed through a nozzle and the end result is perfect mixed glue which dries in a few hours (polyester) or overnight (epoxy). If you are placing a lot of bolts then a glue system is certainly a cost effective method. It is very messy and requires diligent attention to detail and quality control. The easiest way to make an obvious, messy and bad bolt is to try and place rings without practicing first! Of all the systems this one requires reading in detail the manufacturers installation guidelines.