If they are just normal coach screws, they come in various sizes, just like bolts.
There is a standard that is based on shank size to bolt head afaik but it is easier just to try a spanner
So you need to drill a hole for the majority of the shank , but allowing for the thread, then treat it like a nut and bolt. Depending on size , use a socket set or a socket & adaptor on a drill.
Or even just a ring spanner
If you need to find a tradesperson to get your job done, please try our local search below,
or if you are doing it yourself you can find suppliers local to you.
Select the supplier or trade you require, enter your location to begin your search.
Please select a service and enter a location to continue...
Are you a trade or supplier? You can create your listing free at DIYnot Local