Identify the case construction from the watch maker's service information before applying a tool. An edge, groove or decorative notch is not enough evidence by itself. If you cannot identify the opening method, stop and ask a watch repairer.
| Construction | What to establish | Tool category to investigate |
|---|---|---|
| Threaded back | The correct engagement profile and holder | Matching case-back wrench or die |
| Press-on back | The intended opening point and closing method | Appropriate case knife and closing equipment |
| Back retained by small screws | Correct driver and screw arrangement | Suitable precision driver |
| Front-loading or unusual construction | Maker's procedure | Professional service equipment |
Opening is only half the job
Before starting, establish how the back will be refitted and how the seal will be inspected. A closing press is not universal: its supports must suit the case and crystal. Do not improvise with clamps, kitchen knives or pliers.
A case holder helps keep the watch supported. It cannot make an incorrect opener suitable. Protect the finish and ensure the tool sits securely before any attempt. If it slips, the back deforms or excessive force seems necessary, stop rather than increasing pressure.
Water resistance needs a separate check
Opening a watch can void its warranty and its water resistance. Water-resistance testing needs proper equipment. A back that appears firmly closed is not proof of sealing. If you depend on the watch's water resistance, arrange professional service and testing.
Buy after identification
Boley's kit describes separate tools for screwed backs and knife opening. Use that distinction as a category guide, not a reason to buy both. For a battery job, read when to leave battery replacement to a professional before purchasing an opener. Keep screws and seals in labelled compartments and avoid working above an uncovered movement.
Sources & further reading
- Boley: case-opening tools in its watchmaker's kit · Checked 2026-10-25