Where it is a law requirement
In some case, having signs to warn people is mandatory as part of the law. Most electrical and chemical installation require the placement of appropriate stickers, banners or any other sign form to warn people. The manufacturers and installers of such systems adhere to the rules and regulations of their practice. The same applies to public places that where the law prohibits certain things or activities like smoking or hooting.
Places that would expose managers or owners to blame
Another area to use warning signs would be at areas that are likely to cause blame on the administration of an institution. A good example would be to warn people with an appropriate sign that their cars are parked at owner's risk. This helps to wade off any potential legal tussle that would have a victim of loss claiming compensation from the management or owners of a facility.
Areas that need order or authorization
Having order is a measure of professionalism, and making people behave appropriately is one function of a warning. As such, warning signs are appropriate for areas where people should behave in an agreed manner. The signs would act as stern reminders of the impending punishment that awaits those who break the agreed or assumed normal situation. An example of such a sign would be one that says trespassers will be prosecuted'. Such a sign warns people not to enter a restricted zone such as a private property.
All the sign stand functions and areas of application discussed above come into force when the sign used is visible. The person assigned the task of placing a sign under any circumstance must consider how people will view it. A warning sign placed at washrooms to differentiate the gents from the ladies is normally placed at the door. Anyone placing the sign anywhere else risks making it useless. A similar case would be the trespassers warning that has to be clearly visible to a person before he or she breaches the perimeter of the property.
Areas appropriate for the sign's material and design
Sign stands come in several shapes, structures and mechanisms. There are fold up signs suitable for floor placement as commonly used by cleaning personnel to warn people of slippery floors. Others have standard icons and labels, and should be at matching locations such as the washroom. If a sign is not waterproof, then placement should not be on areas that are prone to wetness, such as outdoors or in bathrooms.
This discussion serves to enlighten you on the appropriate places to use warning signs, and with this guidelines, you are free to interpret and place your sign at a location that will let it serve its purpose.