Made in the USA • Patented • Proved Worldwide
What Is JAWS® Large?
JAWS® Large is a stay-in-place concrete screed chair designed to support 1.5″ to 2.0″ wide aluminum, magnesium, or steel screed rails for accurate grade control and consistent screed setup.
The patented JAWS® “teeth” hold the screed rail securely during placement and release easily when moving down the pour line. The internal “fins” hug the mounting structure so the chair will not bounce off rebar or rod during placement.
Designed For
- Slab-on-grade construction
- Elevated slabs
- Concrete overlays
- Vapor barrier slabs
- Bridge decks and infrastructure projects
- Super flat floors requiring FF/FL compliance
- Industrial and commercial flooring
Why Contractors Choose It
- Designed for wider 1.5″–2.0″ aluminum, magnesium, or steel screed rails
- JAWS “teeth” hold rail securely yet release easily as you move down the pour line
- Internal fins hug rebar/rod to prevent bounce-off during placement
- Non-conductive and non-corrosive for harsh environments
- Virtually unbreakable under normal placement conditions
How It Works
- Set your grade. Set a string line or laser level set to the final, finished elevation of concrete. When using the MAKO Driver with the JAWS Large and a 2” metal or magnesium rail (actual height 4”) lower the string line 2.1 inches below finished slab elevation. This adjustment compensates for the extra height of the 2” rail so the top of the screed aligns with finished slab elevation. Be sure to confirm the actual height of your rail compared and calculate string line or laser heights.
- Choose your mounting structure. Use 1/2" rebar, all-thread, or similar (3/8"–5/8" also works). The internal fins in the chair grip the mounting structure and hold it in place.
- Load the assembly. Insert mounting structure into the JAWS Large, then place the MAKO Driver over it.
- Drive to height. Drive with a mallet until the Driver marker aligns with the string line. Now your screed supports are set at the proper height to accept the screed.
- Repeat spacing. Install screed supports every 3–4 feet along the screed run.
- Set your screed rail. Place a 2” aluminum or magnesium screed onto the JAWS Large screed chair supports. Your screed rail is now set at grade.
- Place and screed. Strike off concrete, move pipe forward, fill the void with mud, and bull float over.
- Leave in place. JAWS Large stay embedded in the concrete—no removal, no disruption to the slab.
Key Specifications
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Supports: 1.5″–2.0″ aluminum, magnesium, or steel screed rails
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Fits Mounting Structures: 3/8″–5/8″ (1/2″ recommended)
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Overall Height: 3.50″
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Minimum Height: 5-1/2″ (140 mm) using 2″ rail
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Spacing: 3–4 ft depending on conditions
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Installation Tool: MAKO Driver
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Material: Impact-resistant medical grade polypropylene
- Non-conductive and non-corrosive
- Made in USA
Frequently Asked Questions
What rail sizes does JAWS Large support?
JAWS Large is designed to support 1.5″ to 2.0″ aluminum, magnesium, or steel screed rails.
What mounting structures can be used?
JAWS Large fits mounting structures from 3/8″ to 5/8″ including rebar, threaded rod, stakes, dowels, PVC, or conduit.
How far apart should JAWS Large be spaced?
Typically every 3–4 feet depending on rail length, screed weight, and sub-grade conditions.
Can JAWS Large be left in the slab?
Yes. JAWS screed chairs are designed as stay-in-place forms made from medical grade polypropylene and will not corrode.
Can it be used with hand or mechanical screeds?
Yes. JAWS Large works with both hand and mechanical screeds.
Downloads
JAWS Large Product Data Sheet
