Forklifts In Use Warning Sign - Choose The Size & Material warning signage, forklifts in use - select the size and material from the list of available options below. Dimensions Material DETAILS Choose from a range of styles, with a choice of size and material available to suit your needs. Forklifts In Use warning sign - used to alert workers and the general public of hazards or a hazardous condition. Warning and highlighting that a hazardous conditions could be life-threatening hazard. A warning sign lets you know that a potentially hazard condition maybe not seem dangerous, but that you could still get hurt. This warning signs displays a black hazard symbol on a yellow background. A black triangle encases the hazard symbol. Black lettering with the words Forklifts In Use are displayed on this sign