This 4" Industrial Floor Lock is designed to work with our 2" wide Industrial Casters with a 5-5/8" (5.625") overall height. Floor locks provide positive braking and locking to a mobile cart. By extending the floor lock, a rubber pad engages directly with the floor (the extended height is slightly larger to ensure positive engagement with the floor). When engaged the rolling stock is locked in position. Typically only one floor lock is required when used with a swivel and rigid corner caster cart configuration (best placement is in between swivel casters), but floor locks can also be used in combination with only swivel and/or brake casters (we offer both swivel and rigid brake casters for added locking safety). When used with all swivel casters, two floor locks are recommended (placed on opposite sides of longer sections of cart). Our industrial floor locks are also available in 5", 6" (for both 7.25" and 7.5" caster heights), and 8" sizes. All feature a 4" x 4-1/2" top plate and are zinc plated, as are our 2" wide Industrial Caster solutions that provide lasting performance benefits.