This bottle has a projection or "latch" from its neck, just below the thread, and along and near the lower end of that thread. There is a gap in the cap thread, that lines up with the "latch" when the cap is fully screwed on. The cap deforms when screwed on, passing the "latch" over the end of the cap thread and into the gap. The "latch" then resists cap removal. Only torque beyond the ability of a small child (or even requiring use of a tool) frees the cap. A second projection from the neck, a "flag", is breakable. It is below the bottom end of the neck thread, just above (measured along the thread) the "latch". The "flag" can fold against the neck, but springs out if released. It catches in the cap-thread gap when the cap is unscrewed, and is torn off or broken by forcible removal of the cap. Its removal or breakage evidences that the bottle has been opened.