Safety Sign: Caution Men at Work Overhead (CAU02) - Mandatory PPE Required. Protect your workers with MV5 Gloves, MV3 Hard Hat, MV7 Safety Shoes, MV25 Reflector Vest, and ensure compliance with company regulations by customizing these mandatory signs. Add your company details below. This black and yellow ABS or Chromadek safety sign is a must-have for any construction site.