There are a lot of rules in the Giver. The rules help to control the population and make sure that the "sameness" is as effective as possible. Basically, there is a rule for everything, no matter how silly it may seem.
For example: Bicycles are to be given to children when the child has his or her ninth birthday. Children are not allowed to ride bicycles before then. This is an interesting rule that the author tells the reader, because this is one of the rules that just about everybody breaks.
Another rule is about family size and structure. Each "family unit" is allowed two children. One male and one female.
Or try this one: It was against the rules to see anybody naked, except babies or old people. And if you did see someone naked, you had to apologize.
There is a rule about not taking anything from the playground area. There is a rule about eating your snack and not taking any of it home for later. There are rules that direct what clothes are to be worn at specific ages. There are rules about how many volunteer hours must be completed by age 12 (that's right, mandatory volunteering). Lots and lots of rules.