Fixing a non-flexible liner:

1. The important thing is not to leave any voids beneath the liner, as when it is filled with water it will be strained and may crack.

2. Try to dig a hole to match the shape of the shell, allowing for at least 25 mm of sand all round. When you have achieved this, shovel a small amount of sand all around the excavation.

3. By placing and removing the shell you will be able to see all the places where the sand has touched the shell allowing you to build up the sand in areas where it has not touched.

4. By repeating this procedure of adding and removing sand, the bottom section of the shell should sit evenly on a bed of sand.

5. When you are satisfied that no more can be done by this method finally place the shell and fill up the voids at the side using a stick to push the sand and compact it.

6. When the edges are nearly full put a hosepipe into the sand and when the area is soaking compact the sand where you can fill any remaining voids.

7. It is then safe to fill the pond.