Working with Aggressive Children

Frequently in my experience I have become involved with aggressive and violent children in the schools. Often times these children need to be removed physically from the setting to protect their safety or the safety of others. My district does not have a "restraint and removal" policy but goes with the "use your best judgement" plan. I am wondering how many other people are dealing with similar children, and what if any your district restraint and removal policies are. Do you have a "time out" room? How is it utilized? Have you had to restrain aggressive children?