A spreading device includes a blade, a control structure mounted on the blade, and an operation handle unit connected with the control structure. The control structure includes a base locked onto the blade, a driving stand formed on the base, a limit stand formed on the base, a pivoting support pivotally connected with the limit stand by a screw member, a control rod mounted on the pivoting support, a cam seat secured on a first end of the control rod, a driving rod having a first end pivotally mounted on the driving stand and a second end pivotally connected with and located at an eccentric position of the cam seat, and an elongate push bar having a first end mounted on a second end of the control rod and a second end securely connected with the operation handle unit.

A concrete float, float assembly, float adapter and interface, and float vibration apparatus and methods are described. A concrete float has improved surfaces, and structures for controlling flow of wet concrete. An interface such as may be included in a quick attach/release configuration may be integrated on a float, and/or may be added onto a float for quick attach/release of a pivot assembly. Adapters may ease attachment or release of an assembly, and may be an interengaging element, such as a sliding dovetail as an interengaging element, or an adapter may be used to place an assembly in tension to secure the assembly. A vibration assembly may be included and configured to have a low center of mass, can have a user display, an accelerometer, and/or other components. A pivot assembly may be included for easier use by an operator, and may include a user display, quick release mechanisms.