FITTING A NEW TOILET SEAT
You can rarely repair a damaged toilet seat satisfactorily — it is usually easier to replace it. Seats and lids are normally sold as a set, though some manufacturers will supply them separately.
1. To fit a new seat. You need to bolt it through the existing holes in the back of the pan rim. Check the diameter of the bolts and the distance between them (if this is not adjustable) to make sure the new seat will fit your pan.
2. If the damaged seat is bolted into place with metal bolts which are rusted over, you will need to soak them in penetrating oil before trying to remove them. Modern units are fitted with plastic bolts which will not rust and should always be tightened only finger tight.
A common problem in many lavatories is that the seat fails to stay up as the cistern sticks. Out too far. If you have this problem, ask whether you can get a cranked fixing bolt for the new seat.
This allows the seat to be moved forwards by up to 50mm, while using the existing holes in the pan rim to bolt the fittings securely in position.