Molly Bolts vs. Wedge Anchors
Comparing 2 standards across 13 specifications. 13 key differences identified.
The Hollow Wall Anchor (Molly Bolt, patented by George F. Croessant in 1934) is an all-metal expansion fastener featuring a slotted steel sleeve that permanently crimps into 4 outward-flaring legs behind hollow drywall or plaster. Unlike toggle bolts, the anchor sleeve remains permanently clamped to the wall, allowing the machine screw to be removed and re-inserted repeatedly.
The Concrete Wedge Anchor (Through-Bolt / Expansion Stud Anchor / Trubolt) is a heavy-duty structural masonry fastener consisting of a solid threaded steel stud with a reverse-tapered conical mandrel and an independent stainless steel expansion clip collar. Driven into solid cured concrete, tightening the upper nut draws the mandrel up into the clip, locking the anchor permanently under thousands of pounds of structural load.
Specification Comparison Table
13 Parameters| Parameter / Spec | ||
|---|---|---|
|
Sleeve Material
|
Pre-slotted zinc-plated cold rolled steel sleeve with barbed anti-spin collar | — |
|
Internal Machine Screw Thread
|
M4, M5, M6 (Metric) or 1/8", 3/16", 1/4" (Imperial) | — |
|
Grip Range Sizing
|
Short (1/8" to 3/8" wall thickness), Medium (3/8" to 1/2" drywall), Long (5/8" to 1" double-drywall/lath) | — |
|
Permanent Retention
|
Yes (Sleeve stays permanently crimped into the wall when screw is removed) | — |
|
Setting Method
|
Tightening the screw with a screwdriver or using a specialized manual Molly setting plier tool | — |
|
Safe Shear Load (1/2" Drywall)
|
Up to 50 lbs (23 kg) shear per anchor | — |
|
Structural Certification
|
— | ICC-ES (International Code Council) cracked & uncracked concrete approval / ACI 318 |
|
Anchor Diameter Range
|
— | 1/4", 3/8", 1/2", 5/8", 3/4", 1" (or M6, M8, M10, M12, M16, M20, M24) |
|
Substrate Limitation
|
— | Solid uncracked/cracked cured concrete ONLY (Unsuitable for brick, hollow block, or mortar) |
|
Installation Style
|
— | 'Through-fixture' installation (Drill hole directly through the metal baseplate into concrete) |
|
Expansion Mechanism
|
— | Tapered conical stud mandrel expands stainless steel clip ring into concrete borehole |
|
Ultimate Tension Capacity (1/2" Anchor)
|
— | 4,000 to 6,500+ lbs (18 to 29 kN) in 4,000 psi concrete |
|
Primary Applications
|
— | Automotive 2-post lifts, structural steel column baseplates, seismic heavy machinery hold-downs |