Bowl Guard
A plastic or wire housing around the top of the bowl, the guard prevents hands, clothing, or foreign objects from coming in contact with the agitator during mixing, and most mixers are required to include one to comply with OSHA regulations (Standard 29CFR 1910.212).
The primary point to take from this is that your staff should understand the dangers of operating the mixer; for example, trying to bypass the guard by putting hands / fingers / utensils in or under it during operation can have very negative consequences and your training should teach the dangers of such things.