drop balls not shown towards an opening 314 proximal to the wall of the central fluid passage 304 as shown the opening 314 provides access to the nozzle inlets 302 of the drill bit 22 the guide slots 312 are formed having a width less than the diameter of the drop balls this configuration allows the drilling fluid to pass through the guide slots 312 to reach the nozzle inlets 302 while preventing the drop balls from passing through a directional surface 316 leads the drop balls through the opening 314 and towards the nozzle inlets 302 thus in this example the directional surface 316 slopes in a direction opposing the sloped top surface 310 other suitable configurations and arrangements for leading the drop balls towards the drill bit nozzle inlets are also contemplated when the one or more drop balls encounter the nozzle inlets 302 the nozzle inlets become plugged u2014 preventing the ejection of drilling fluid thus plugging the nozzle inlets 302 restricts the flow of the drilling fluid through the bottom hole assembly 10 the flow restriction causes a hydraulic pressure increase in the drilling fluid up stream of the restriction in this example the grate actuation assembly 300 further includes a gate structure 318 partitioning the area of the central fluid passage 304 near the nozzle inlets 302 creating a protected area 320 the gate structure 318 prevents the drop balls from entering the protected area 320 and.