§1. The Most Holy Eucharist is to be reserved habitually in only one tabernacle of a church or oratory.
§2. The tabernacle in which the Most Holy Eucharist is reserved is to be situated in some part of the church or oratory which is distinguished, conspicuous, beautifully decorated, and suitable for prayer.
§3. The tabernacle in which the Most Holy Eucharist is reserved habitually is to be immovable, made of solid and opaque material, and locked in such a way that the danger of profanation is avoided as much as possible.
§4. For a grave cause, it is permitted to reserve the Most Holy Eucharist in some other fit-ting and more secure place, especially at night.
§5. The person responsible for the church or oratory is to take care that the key of the tabernacle in which the Most Holy Eucharist is reserved is safeguarded most diligently.
Source: Code of Canon Law (Vatican.va)