Most builders agree that blocking a Lally column for sheetrock or paneling is way too time-consuming. These nifty plastic collars let you block out common steel columns quickly and easily. The hinged halves of the collar fit around the column and simply screw together with the included screw. Color-coded yellow collars fit 3" or 3-1/2" columns, while blue collars fit 4" columns. Hinged plastic shim tabs adjust for column diameter. Collars should be mounted on 24" centers to provide adequate panel or sheetrock support; most eight-foot ceiling height applications require 5 collars. Made in the USA.