What feature must handheld power tools without means to securely hold accessories have?

Handheld power tools that lack a means to securely hold their accessories must incorporate a constant-pressure switch. This safety feature is crucial because it ensures that the tool only operates while the switch is actively held down by the user. Such a design mitigates the risk of accidental activation, which could lead to dangerous situations or injuries if the tool were to continue running after being unintentionally dropped or released.

In contrast, a manual switch may not provide the same level of safety, as it could be accidentally turned on or off without consistent user control. A trigger lock is beneficial for preventing unintended activation; however, it does not provide continuous control, which is critical in tools where accessory security is an issue. Lastly, a detachable handle does not directly address the need for controlling the activation of the power tool during use, making it less relevant in this context. Therefore, a constant-pressure switch effectively addresses the unique hazards associated with handheld tools that lack secure accessory holding mechanisms.