Slate is one of the best types of roofing material available, but occasionally the odd slate on your roof will crack or slip and will need to be replaced. You can get a roofing firm to do the job for you, but if you have access to your roof and feel confidant, you can replace the slate yourself.
There are a couple of methods you can use to replace a broken slate.
Slate hook
You can use a small device called a slate hook to hold a new slate into position. You simply have to nail the hook into the slot between the under-slates pushing the hook into the slots. You then just need to slide the new slate into position making sure it's fitted over the hook.
Nail and bib
Use a slate ripper to remove the damaged slate then slide a new slate into position. Nail the slate into place between the slot of the two slates above the new slate. You can then slide the bib flashing under the new slate and over the nail head to stop leaks.