Steel Dog SCL coil lag

For securing formwork to timber structures

  • 3/4″ hex head lag bolt with swiveling loop coil tie
  • Available for 1/2″ coil rod or 1/2″-13NC machine thread
  • Useful for one-sided walls against wood lagging
  • 3000 lbs Max. Safe Working Load (see load tables)

The Steel Dog® Coil-Lag™ is designed to provide a temporary means of attaching formwork to wood timbers. Typical application: one-sided forming against soldier piles with wood lagging, or other timber retaining walls.


  • Standard hex head lag bolt for socket wrench or powered driver installation.
  • Swivel loop coil tie end to accommodate misalignment between lag bolt placement and formwork tie location.
  • Accepts standard ½”coil rod or ½”-13 NC rod (SCL-4NC)
  • Less expensive than toggle ties, and doesn’t require clear space behind timber (compacted fill not a problem).
  • Eliminates expensive external bracing or welding.


Bolt is ASTM A307. Swivel loop wire is AISI C1038.
FINISH None. Zinc coatings available: consult factory.
MAXIMUM SAFE WORKING LOAD 3000 Lbs. (2-to-1 safety factor). Actual Safe Working Load will depend on pull-out strength of lag in wood and off-axis loading angle. See tables at right.

Download Coil Lag Spec Sheet



  • Install only into pre-drilled hole (9/16” diameter MAX)
  • Use wax or other suitable solid lubricant on lag bolt threads (especially in hardwood species.)
  • Screw bolt into wood using wrench on bolt hex head only. Do not use swivel loop to turn bolt. If excessive resistance is met, unscrew bolt and re-lubricate or change bolt location. If using powered socket driver (such as right angle drill or impact wrench), apply 400 ft-lb max torque.Bolt must be screwed into wood until swivel loop is just in contact with wood surface.
  • If wood splits when installing lag bolt, the bolt will not hold the rated load. Move bolt location at least 1-1/2” across grain.
  • Swivel loop may be loaded up to 30° off-axis when rotated in “A” direction, and up to 90° off-axis when rotated in the “B” direction (see diagram at right).
  • Generally, the withdrawal resistance of the bolt from the
    wood and the off-axis load angle will determine the allowable tie load on the swivel loop coil. When loading off-axis, (see tables at right), consideration must be given to translation forces or torque on timber element due to lateral bolt loads.
  • Not intended for installation into end grain.