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Adjustable Structural Supports Since 1951.

4x4 Screw Jack

per SJ-4
78 reviews

The Ellis 4x4 Screw Jack is a versatile product that will allow you to create an adjustable support of any length with your own 4x4 lumber.  Use as structural support in residential, commercial, trench and collapse rescue shoring applications.

Availability: In Stock

Item #

safe load capacity

type of finish




15,000 lbs

Powder Coated

12 lb



15,000 lbs

Galvanized Finish

12 lb


Product Overview

The Ellis 4x4 Screw Jack is made with high quality steel and durable enough to last for many years.  All of the Ellis products have been load tested to allow for SAFE load ratings to be determined.  Rest assured knowing that all load capacities seen on the Ellis Manufacturing Co. site include a safety factor of 2.5 to 1 (or better)!   

Demonstration Video

Ellis Screw Jack 4x4 Specifications:

  • 15,000 Lb. Safe Load Capacity!
  • For Vertical / Horizontal Support in residential, commercial, trench shoring and collapse rescue applications.
  • Galvanized or Powder Coated Finish.
  • Use your own Standard with Dressed 4x4 Lumber (3.5" Sq.), cut square to any length.
  • 14.25" Minimum Overall Height (screwed down).
  • Full 6" Adjustment with 1.25" dia. acme threaded screw.
  • Turn "U" Shaped Handle to Adjust Height of Screw Jack. Lift up to 1800 lbs by hand or 4000 lbs. w/ a 2"x4"x6' piece of lumber placed between screw and handle for extra leverage.
  • Screw is Greased for easy tuning and to prevent rusting.
  • Base Plate will not turn with screw and 4 5/16” Diam. holes are provided to secure it to a solid foundation.  Always Secure to a solid foundation.
  • Proper bracing required Prevent lateral shifting.
  • Screw Jack is equipped with a safety lock.  Tighten safety lock with an Allen Wrench once final adjustment has been made to prevent accidental height adjustment to jack post.  (use 6mm allen wrench)
  • 4x4 Heads are available for securing vertical 4x4 to horizontal beam: Purlin Splicer, Joist Holders, Pivoting, T-Head, U-Head.

Maximum Safe Working Loads

Total shore height including SJ-4 Maximum safe load capacity
4' 15,000 lbs.
6' 12,000 lbs.
8' 7,200 lbs.
10' 5,000 lbs.
12' 3,000 lbs
14' 2,600 lbs.
15' 0 lbs.

Load capacity based on actual load test results Douglas Fir #1 4x4 dressed lumber (3.5" square). Capacities include a standard 2.5/1 safety factor. Lumber must be cut square on both ends. Do not exceed recommended allowable safe load ratings in the above chart.  Do not extend screw past advertised adjustment range.

*Caution, the acme screw of the 4x4 GALVANIZED Screw Jack will completely separate from the acme nut if screwed out too far. Do not extend the acme screw past the maximum adjustment of 6". This will insure that the threads of the acme nut will be used to support a heavy load.  For maximum safe load capacity to be obtained, Ellis Screw Jack should be used with a 4x4 lumber cut to at least 5.5" long and subject to support straight loads only. We recommend tightening set screw in the side of the Screw Jack with a 6mm allen wrench prior to loading. Before construction begins it is recommended that you consult with certified structural engineer for approval of our products within your application.

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