OSHA requirements are set by statute, standards and regulations. Our interpretation letters explain these requirements and how they apply to particular circumstances, but they cannot create additional employer obligations. This letter constitutes OSHA's interpretation of the requirements discussed. Note that our enforcement guidance may be affected by changes to OSHA rules. Also, from time to time we update our guidance in response to new information. To keep apprised of such developments, you can consult OSHA's website at https://www.osha.gov.



January 13, 1993

Mr. Steve Nichols
American Roof
21808 N.E. 175th
Woodinville, Washington 98072

Dear Mr. Nichols:

This is in response to your October 20 letter requesting a statement of compliance from the Occupational Safety and Health Administration (OSHA) for the Rope Grab Knot.

Please be advised that OSHA does not have specific standards applicable to construction for knots used in body belt/harness systems. The rope grab knot is addressed in nonmandatory Appendix C to OSHA's general industry standards at 29 CFR 1910.66. Paragraph (h)(8) of Section III of the appendix states in part that due to the significant reduction in strength of the lanyard/lifeline, sliding hitch knots should not be used for lifeline/lanyard connections except in emergency situations where no other available system is practical. However, based on the test results included in your letter, the rope grab knot (three- and-three sliding hitch knot) used as described in the tests, appears to meet the intent of OSHA's related construction standards for lanyards. It should be noted that the knot must be tied with sufficient tension to preclude its sliding too freely on the lifeline. Failure to use proper tension could render the knot ineffective and it would not be in compliance with the intent of the OSHA regulations.

If we can be of any further assistance, please contact me or Mr. Dale Cavanaugh of my staff at (202) 219-8136.


Roy F. Gurnham, Esq., P.E.
Office of Construction and Maritime
Compliance Assistance

October 20, 1992

U.S. Department of Labor
OSHA Division
Washington D.C. 20210

Re; Rope Grab Knot/ Fall arrestor

Attn; Mr. Roy F. Gurnham P.E., Esq.

Find enclosed test data for Rope Grab Knot. OSHA as well as State industrial safety standards specify the use of a "Fall Arrestor" when a worker is tied to a safety lifeline. Arrestors are not specified to be mechanical or non-mechanical devices. In Washington State, we were directed to use a Rope Grab Knot, known by various names such as, "Prussic Knot", and "Triple Sliding Hitch Knot" and I am sure there are other names. We have used this system in our own firm for almost 3 years with very good results.

Recently I tested the Rope Grab Knot for static pull and dead weight drop load free fall tests. Both tests provided excellent results indicating the knot works well and exceeds State safety standards.

I want to know if this system meets U.S. Dept of Labor standards for "Fall Arrestor" non-mechanical device, and if so, I would appreciate a letter of your response. We would like to be able to use this system in other States and really need to know what FED-OSHA has to say about it.

Recently I received a letter form you office regarding our Super Anchor fall arrest bracket, and I want to thank you for your letter. I look forward to hearing from you soon about this very important matter.

If you have any questions or concerns regarding my request, please call me.

Best regards to you, Steve Nichols, presd.






296-155-24501    Scope and Application.
296-155-24503    Definitions.
296-155-24505    Fall Protection Work Plan.
296-155-24510    Fall Restraint, Fall Arrest Systems.
296-155-24515    Guarding of Low-Pitched Roof Perimeters.
296-155-24520    Leading Edge Control Zone.
296-155-24521    Safety Monitor System.
296-155-24525    Appendix to Part C-1, Fall Restraint and Fall Arrest (Employer Information Only).

WAC 296-155-24501, Scope and Application.

This section sets forth requirements for employers to provide and enforce the use of fall protection for employees in construction, alteration, repair, maintenance (including painting and decorating), demolition workplaces, and material handling covered under chapter 296-155 WAC.

WAC 296-155-24503, Definitions.

(1) Anchorage means a secure point of attachment for lifelines, lanyards or deceleration devices which is capable of withstanding the forces specified in the applicable sections of chapter 296-155 WAC.

(2) Approved means, for the purpose of this section; tested and certified by the manufacturer, or any recognized national resting laboratory, to possess the strength requirements specified in this section.

(3) Body belt means a Type 1 safety belt used in conjunction with lanyard or lifeline for fall restraint only.

(4) Full body harness means a configuration of connected straps to distribute a fall arresting force over at least the thighs, shoulders and pelvis, with provisions for attaching a lanyard, lifeline, or deceleration devices.

(5) Full body harness system means a Class III full body harness and lanyard which is attached to an anchorage meeting the requirements of Part C-1 WAC 296-155; or attached to a horizontal or vertical lifeline which is properly secured to an anchorage(s) capable of withstanding the forces specified in the applicable sections of chapter 296-155 WAC.

(6) Catenary line - see horizontal lifeline.

(19) Leading edge means the advancing edge of a floor, roof, or formwork which changes location as additional floor, roof, or formwork sections are placed, formed, or constructed. Leading edges not actively under construction are considered to be "unprotected sides and edges," and positive methods of fall arrest or fall restraint shall be required to protect exposed workers.

(20) Lifeline means a vertical line from a fixed anchorages or between two horizontal anchorages, independent of walking or working surfaces, to which a lanyard or device is secured. Lifeline as referred to in this text is one which is part of a fall protection system used as back-up safety for an elevated worker.

(21) Locking snap hook means a connecting snap hook that requires two separate forces to open the gate; one to deactivate the gatekeeper and a second to depress and open the gate which automatically closes when released; used to minimize roll-out or accidental disengagement.

(22) Low-pitched roof means a roof having a slope equal to or less than 4 in 12.

(23) Positioning belt means a single or multiple strap that can be secured around the worker's body to hold the user in a work position; for example, a lineman's belt, a rebar belt, or saddle belt.

(24) Restraint line means a line from a fixed anchorage or between two anchorages to which an employee is secured in such a way as to prevent the worker from falling to a lower level.

(25) Roll-out means unintentional disengagement of a snap hook caused by the gate being depressed under torque or contact while twisting or turning; a particular concern with single- action snap hooks that do not have a locking gatekeeper.

(26) Rope grab means a fall arrester that is designed to move up or down a lifeline suspended form a fixed overhead or horizontal anchorage point, or lifeline, to which the belt or harness is attacked. In the event of a fall, the rope grab licks into the lifeline rope through compression to arrest the fall. The use of a rope grab device is restricted for fall restraint applications. (Refer to WAC 296-155-24510(2)(b)(iii).)

(27) Safety line - see lifeline.

(28) Safety monitor system means a system of fall restraint used in conjunction with a warning line system only, where a competent person as defined by this part, having not additional duties, monitors the proximity of workers to the fall hazard when working between the warning line and the unprotected sides and edges, including, the leading edge of a low pitched roof or walking/working surface.

(29) Self-retracting lifeline means a deceleration device which contains a drum-wound line which may be slowly extracted from, or retracted onto, the drum under slight tension during normal employee movement, and which after onset of a fall, automatically locks the drum and arrests the fall.

(30) Shock absorbing lanyard means a flexible line of webbing, cable, or rope used to secure a body belt or harness to a lifeline or anchorage point that has an integral shock absorber.

(31) Single-action snap hook means a connecting snap hook that requires a single force to open the gate which automatically closes when released.