Knots connect climbers to ropes, ropes to trees, and loads to lowering systems. A properly tied knot holds under load and releases when needed. A poorly tied knot fails under stress, potentially killing workers or dropping loads. Mastering essential knots is non-negotiable for professional tree work.
Knot Fundamentals
Understanding knot behavior prevents failures.
Strength Reduction occurs at every knot. Knots create stress concentrations where rope bends sharply. Most knots reduce rope strength by 30-50%. A rope rated at 6,000 pounds breaking strength may fail at 3,000-4,000 pounds at the knot.
Working End vs. Standing End terminology distinguishes the free end used to tie the knot (working end) from the loaded portion of the rope (standing end).
Dressing the Knot means arranging all strands properly before loading. Twisted, crossed, or improperly seated strands weaken knots significantly.
Setting the Knot involves loading the knot enough to tighten all components before full application. Unset knots can shift and fail under full load.
The Bowline: Fundamental Fixed Loop
The bowline creates a non-slip loop that holds under load and unties relatively easily afterward.
Applications:
- Tying into climbing systems
- Creating anchor points
- End-of-line attachments
Tying Method:
- Form a small loop in the standing end (the “rabbit hole”)
- Pass the working end up through the loop (rabbit comes out of hole)
- Pass the working end around behind the standing end (around the tree)
- Pass the working end back down through the small loop (back into hole)
- Dress and set
Critical Points:
- Working end must be inside the main loop, not outside
- Adequate tail (6+ inches) should remain after tying
- A backup stopper knot adds security
- The bowline can work loose if not loaded; not ideal for shock loads
Friction Hitches: Adjustable Grip
Friction hitches grip rope when loaded but slide when unloaded, allowing adjustment.
Blake’s Hitch is widely used in arborist climbing:
- Wrap working end around rope 3-4 times, moving down
- Continue wrapping back up 2 times
- Pass working end through the original wraps
- Exit out the bottom of the knot formation
Tautline Hitch provides similar function with different construction. Often taught to beginners for its simplicity.
Distel Hitch offers smooth operation and good grip on many rope combinations.
Valdotain Tresse (VT) uses two ropes wound together for a smooth, reliable friction hitch.
Selection Factors:
- Rope combination (climbing line diameter vs. accessory cord diameter)
- Grip requirements (heavier climbers may need more wraps)
- Release characteristics (some release smoother than others)
- Personal preference developed through experience
The Running Bowline: Choker Configuration
A bowline tied around its own standing end creates an adjustable choker.
Applications:
- Setting climbing line on branches
- Creating rigging anchor points
- Temporary choker attachment
Behavior:
- Loop tightens under load
- Releases tension when load is removed
- Slides on standing end to adjust position
Caution: The running bowline can bind tightly under heavy load, making retrieval difficult. Not ideal for heavy rigging where release is needed.
The Clove Hitch: Quick Attachment
Two simple loops create a clove hitch that holds well when loaded perpendicular to the rope.
Applications:
- Attaching to carabiners
- Temporary line attachment
- Quick adjustable positioning
Limitations:
- Can slip on smooth surfaces
- Works best with load perpendicular to attachment point
- Not suitable as sole attachment for life safety
Advantages:
- Fast to tie and untie
- Easily adjustable while in place
- Works well for intermediate attachment points
The Timber Hitch: Load Attachment
The timber hitch grips cylindrical objects securely under tension.
Applications:
- Attaching lowering lines to branches and trunk sections
- Securing logs for dragging or lifting
- Temporary attachment to round objects
Tying Method:
- Pass rope around the object
- Pass working end around standing end
- Wrap working end around itself 3-5 times
- Apply load to set
Half Hitch Addition: Adding one or two half hitches above the timber hitch helps control load orientation during lowering.
The Prusik Knot: Emergency Ascent
The prusik knot grips rope when weighted but slides when unweighted.
Applications:
- Emergency ascent on fixed line
- Creating progress capture in hauling systems
- Backup for mechanical devices
Tying Method:
- Use loop of accessory cord
- Wrap around climbing rope 3-4 times
- Pass entire loop through itself
- Dress wraps neatly, parallel
Operational Notes:
- Grips when loaded, slides when unloaded
- May glaze (melt) under rapid sliding; not a descent device
- Cord diameter should be significantly smaller than rope (typically 7-8mm cord on 11-13mm rope)
The Figure Eight Family
Figure eight variants serve multiple purposes.
Figure Eight on a Bight creates a strong fixed loop mid-line without access to rope ends.
Figure Eight Follow-Through creates a strong end loop directly tied around anchor points.
Figure Eight Bend (Flemish Bend) joins two ropes securely.
Characteristics:
- Strong (60-70% rope strength retained)
- Easy to verify correct tying
- Can be difficult to untie after heavy loading
Practice and Proficiency
Knot competence requires regular practice.
Learning Sequence:
- Learn to tie each knot slowly and correctly
- Practice until correct tying is automatic
- Practice in gloves (you’ll be wearing them on the job)
- Practice in awkward positions simulating actual work
- Maintain skills through regular use
Verification Habits:
- Check every knot after tying
- Dress and set before loading
- Verify tail length adequate
- Double-check life-safety connections
When In Doubt: If uncertain whether a knot is correct, untie and retie. The seconds spent verifying prevent catastrophic failure.
Sources:
- Knot specifications: ISA arborist rigging manual
- Strength reduction data: Equipment manufacturer testing
- Friction hitch analysis: Professional arborist research publications
- Safety standards: ANSI Z133 knot requirements