Having been lying on the sofa like a couch potato for most of my resting time, I began to experience some backache. The more than 3 years old sofa has a sinking base due to some years of usage and to solve the problem I have a plank of plywood cut out to fit the base below the cushions. This idea was brought up by one of my bro-in -law on one of his visits. Thanks to you, Pik Lee. Now I do not have to suffer anymore backache or difficulty in getting up from the firm sofa. So if any of you have any sinking sofa, try to get a plywood from your carpenter with the correct measurement and it will save you some dough instead of throwing it away.