What does the Huizi symbol on a handheld power tool mean?

That is the double insulation mark on the handle.

Handheld Power Tools Class I Tools:

Tools not only rely on basic insulation for protection against electric shock, but it also incorporates an additional safety precaution by placing Conductive parts are connected to protective (grounding) conductors in installed fixed circuits in such a way that accessible conductive parts do not become live in the event of damage to basic insulation.

Class II tools:

The rated voltage exceeds 50V. Tools not only rely on basic insulation for protection against electric shock, but it also provides the additional safety precautions of double insulation or reinforced insulation and measures that do not have a protective earth or are dependent on the conditions of the installation. This type of tool shell has two types: metal and non-metal, but the hand-held part is non-metal, and the non-metal part is marked with a "return" symbol.

Extended information:

Notes

The power cord of Class I tools must be three-core (single-phase tools) or four-core (three-phase tools). Stranded copper core rubber sheathed wire, the yellow and green two-color wire can only be used as protective grounding or neutral wire under any circumstances.

Safety isolation transformers for Class III tools, leakage protectors for Class II tools, and control boxes and power adapters for Class II and III tools should be placed outside, and designated personnel should be assigned to monitor them outside.

The flexible cables that come with handheld power tools are not allowed to be removed or extended at will, and the plugs are not allowed to be removed and replaced at will.

Before use, check whether the tool shell, handle, zero connection (ground), wires and plugs, switches, electrical protection devices and mechanical protection devices, and the rotating part of the tool are normal.

When using power tools, do not hold the wire or the rotating part of the tool by hand. During use, you must prevent the wire from being twisted, damp, heated or damaged.

It is strictly prohibited to insert the wire core directly into the socket or hang it on the switch.