Locks are your 1st line of defence against trespassers and intruders. If it opens we recommend lock it. The main areas to consider ones are doors windows gates including out buildings.
Locks do not mean you have to carry big bunches of keys. Locks can be electronic with remote control or if preferred with card access or keyed alike ie one key fits all. Some locks even have a combination option and now biometric is becoming more available.
Lock come in all shapes and sizes but all designed with a specific purpose in mind. The easy option get TN2 security to carry out a security risk assessment.