Abstract: This invention relates to a plug bolt (1) and more specifically, but not exclusively, to a plug bolt (1) for use with a device such as an air-cooled heat exchanger. One of the problems with conventional plug bolts is that when the bolts are over tightened, it may damage the thread of the device it is installed in. Once the thread is damaged it has to be repaired, causing downtime, or where it is not possible to repair, the device will have to be replaced. It is accordingly an object of this invention to provide a plug bolt (1) which, at least partially, alleviates some of the problems associated with the prior art. It is envisaged that the invention will provide a plug bolt (1) which fails before it is overtightened to prevent damage, is easy to manufacture, and is as simple to use as the prior art.