Made in the USA • Patented • Proved Worldwide
What Is the Adjustable JAWS® RailFin Concrete Screed Support System?
The Adjustable JAWS® RailFin Concrete Screed Support Systemis a complete bundled MAKO system designed for fast, accurate grade setting using 1/4″ flat rolled steel screed rails.
This kit combines JAWS® RailFin Screed Chairs, FinStand® Adjustable Supports, and Base Plate 4.5® to create a stay-in-place, height-adjustable screed support system for vapor barriers, concrete overlays, sand/rock subgrades, elevated decks, sloped slabs, bridge work, and super flat floor projects. Threaded rods (all-thread), hex nuts, and flat washers are sold separately.
Designed For
- Vapor barrier slabs (membrane-safe Base Plate)
- Concrete overlays
- Slabs on sand or rock sub-grade
- Elevated decks (wood or metal)
- Sloped slabs and grade transitions
- Bridge decks, waterways, and power plant projects
- Super flat floors requiring FF/FL compliance
- Flat rolled steel rail screed systems
Why Contractors Choose It
- Complete adjustable flat-rail screed system including vapor barrier-ready Base Plate
- Stable setup on membranes, overlays, sand, and rock
- Precise grade control for sloped or elevated slabs
- Non-conductive and non-corrosive for extreme environments
- Engineered for consistent results on super flat floors
How It Works
- Set your grade. Run a string line or laser at finished slab elevation.
- Establish your screed line. Snap a chalk line for a wood deck or follow flute on a metal deck. For use on vapor barrier use a rebar to setup and adhere with adhesive. Space supports every 3–4 feet.
- Install Base Plate + FinStand. Snap together and secure to deck or adhere to vapor barrier.
- Cut your threaded rod. Cut based on slab depth. (Use steel all-thread for slabs over 6".)
- Secure the FinStand + Base Plate Assembly. Fasten to deck - use screws on metal deck or nails on wood deck. Be sure the FinStand+ Base Plate sits flat and solid.
- Install threaded rod. Thread into FinStand (minimum 1/2" embedment).
- Install the JAWS RailFin Place on threaded rod (minimum 1" embedment).
- Adjust to height. Adjust the threaded rod in the FinStand until the top of the threaded rod sits 2.25" below the string line. A nut or washer can be added for fine tune adjustments.
- Repeat spacing. Install screed supports every 3–4 feet along the screed run.
- Set your screed rail. Place a flat rolled steel screed rail onto the JAWS RailFin supports. Typical rail dimensions 1/4" thick x 2" high x 10 ft long. The rail should now sit exactly at finished slab elevation.
- Place and screed. Strike off concrete with hand or mechanical screed, slide screed rail along screed chairs, fill the void with mud, and bull float over.
- Leave in place. JAWS RailFin assembly stays embedded in the concrete—no removal, no disruption to the slab.
Key Specifications
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Screed Rail Supported: 1/4″ flat rolled steel rail (commonly 1/4″ x 2″ or 1/4″ x 2-1/2″)
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Threaded Rod: 1/2″-13 all-thread (cut to slab depth)
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Vertical Adjustment: Up to 1-3/4″ (45 mm) using nut and washer
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Base Plate: Membrane-safe, non-penetrating design
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Spacing Guideline: 3–4 ft depending on conditions
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Material: Impact-resistant medical grade polypropylene (non-metallic)
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Coverage: Approx. 3,000 sq ft per box
Full Specifications
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Includes: 100 JAWS® RailFin Screed Chairs
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Includes: 100 FinStand® Adjustable Supports
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Includes: 100 Base Plate 4.5®
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Screed Rail Supported: 1/4″ flat rolled steel rail (commonly 1/4″ x 2″ or 1/4″ x 2-1/2″)
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JAWS Mounting Range: Fits rebar or rod 3/8″–5/8″ (10–16 mm)
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Threaded Rod: FinStand uses 1/2″-13 all-thread (cut to length based on slab depth)
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Vertical Adjustment: Up to 1-3/4″ (45 mm) using nut and washer
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Spacing Guideline: Place supports every 3–4 ft (1 m)
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Minimum Assembly Height: Using a 1/4″ x 2-1/2″ flat rolled steel rail from the bottom of the Base Plate to finished elevation is approximately 5-3/4″ (146 mm)
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Load Capacity: Holds up to 1,000 lbs (system-dependent)
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JAWS RailFin Feature: Internal “fins” hug rebar/rod to prevent bounce-off during placement
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Base Plate Feature: Will not puncture vapor barrier; textured underside grips adhesives; can be secured with screws, nails, or construction glue
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Material: Impact-resistant medical grade polypropylene (non-metallic)
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Coverage: 100 RailFins + 100 FinStands + 100 Base Plates per box (approx. 3,000 sq ft / 278 m²)
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Rod Guidance: Use steel threaded rod for slabs over 8″ (200 mm)
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Threaded Rod / Hardware: Sold separately. Rod length determines finished slab height (see slab depth chart)
Compliance & Approvals
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Standards: ACI 302.1R-04, ACI 117, ASTM E1155
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Approvals: Iowa DOT approved (other states pending)
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Patents: 8,096,182 | 8,544,182 | Patent Pending
Additional Notes
- Threaded rods (all-thread), hex nuts, and flat washers are sold separately
- For slab depth and all-thread length selection, refer to the FinStand slab depth chart
- For slabs over 8″ (200 mm), steel threaded rod is recommended
- The MAKO® Driver is not designed to work with JAWS® RailFin chairs
Frequently Asked Questions
Does this kit include threaded rod, nuts, and washers?
No. Threaded rods (all-thread), hex nuts, and flat washers are sold separately.
Can this be used on vapor barriers without puncturing the membrane?
Yes. Base Plate 4.5 is designed to sit on vapor barriers without puncturing them.
How far apart should supports be placed?
Typically every 3–4 feet depending on rail length and sub-grade conditions.
Does the MAKO® Driver work with JAWS® RailFin?
No. The MAKO® Driver is not designed to work with JAWS® RailFin chairs.
Downloads
JAWS® RailFin Product Data Sheet
FinStand® Product Data Sheet
Base Plate 4.5® Product Data Sheet
