You can break, repair, and bypass mechanical devices.
Check: you can disable mechanical devices and traps (as per the Disable Device skill description in the 3.5 PHB) and open locks without the proper key (as per the Open Lock skill description in the 3.5 PHB). The DC to disable or break a lock is 10 less than the DC to open it.
Repair: you can also repair mechanical devices. In general, simple repairs have a DC of 10 to 15 and require no more than a few minutes to accomplish. More complex repair work has a DC of 20 or higher and can require an hour or more to complete. Making repairs also involves a monetary cost when spare parts or new components are needed, represented by a Wealth check. If the GM decides this isn't necessary for the type of repair the character is attempting, then no Wealth check is needed.
| Repair Task (Example) | Purchase DC | Tinker DC | Time |
| Simple (tool, basic weapon) | 4 | 10 | 1 minute |
| Moderate (counterlever) | 7 | 15 | 10 minutes |
| Complex (windmill) | 10 | 20 | 1 hour |
| Advanced (mechanical clock) | 13 | 25 | 10 hours |
Jury-Rig: you can choose to attempt jury-rigged, or temporary, repairs. Doing this reduces the purchase DC by 3 and the Repair check DC by 5, and allows you to make the checks in as little as a full-round action. However, a jury-rigged repair can only fix a single problem with a check, and the temporary repair only lasts until the end of the current scene or encounter. The jury-rigged object must be fully repaired thereafter. The jury-rig application of the Tinker skill can be used untrained.
Try Again?: Yes, though in some specific cases, the GM may decide that a failed Tinker check has negative ramifications that prevent repeated checks.
Special: A character can take 10 or take 20 on a Tinker check. When making a Tinker check to accomplish a jury-rig repair, a character can't take 20. Tinker requires a tool kit or a multipurpose tool, depending on the task. If the character does not have the appropriate tools, they take a -4 penalty on the check.
Synergy: 5 or more ranks in a Craft skill related to the object being tinkered with gives you a +2 bonus to Tinker checks. This bonus increases by +1 for every additional 10 ranks (that is, +3 at 15 ranks, +4 at 25 ranks, and so on).
Time: See the table for guidelines. A character can make a jury-rig repair as a full-round action, but the work only lasts until the end of the current encounter.
Feat: the Tinker With Magic feat allows you to use this skill to disable, bypass or repair magic traps.