a. have a robust structure; b. not give rise to any additional risk; c. not be easy to move or render inoperative; d. be located at an adequate distance from the danger zone; e. not unnecessarily restrict the view of the work equipment's work operation; f. not obstruct necessary work such as installation, replacement of parts and maintenance. Access shall be limited to the area where such work is to be carried out and, if possible, not involve the removal of protective guards or devices.