1. mechanic's lien, this is only a temporary lien, it does not require a formal judgement, they can file a lien against your property, as long as they can show proper notice on billing or delivery schedule.
2. judgement lien, if the other side really want to block your sale, all they need to do is file a claim against your property, your sale will not able to close, pending on further judgement.
sorry to tell you that.