Hi Roxy,
I am having a problem getting my G29 to probe four points only. This is the BeckDac fork from about 15 months ago. If it would help to update to newer marlin I could do so.

I have the following in configuration.h. Thanks for any help!

Code:
#define AUTO_BED_LEVELING_GRID  // with AUTO_BED_LEVELING_GRID, the bed is sampled in a
  // AUTO_BED_LEVELING_GRID_POINTSxAUTO_BED_LEVELING_GRID_POINTS grid
  // and least squares solution is calculated
  // Note: this feature occupies 10'206 byte
#ifdef AUTO_BED_LEVELING_GRID


    // set the rectangle in which to probe
    #define LEFT_PROBE_BED_POSITION 0
    #define RIGHT_PROBE_BED_POSITION 110
    #define BACK_PROBE_BED_POSITION 195
    #define FRONT_PROBE_BED_POSITION 0


    // set the max number of grid points per dimension
    // The G29 command defaults to 3 if nothing is specified.  But setting the number of probed 
    // points higher is very useful when getting a Bed Topology Report  (G29 n 5 T)
    #define AUTO_BED_LEVELING_GRID_POINTS 2


    // Uncomment one of the following four lines so the Bed Topology Report can produce a map
    // that relates accurately to your bed orientation.  


    //#define ORIGIN_FRONT_LEFT
    //#define ORIGIN_BACK_LEFT
    //#define ORIGIN_FRONT_RIGHT
    #define ORIGIN_BACK_RIGHT


  #else  // not AUTO_BED_LEVELING_GRID
    // with no grid, just probe 3 arbitrary points.  A simple cross-product
    // is used to esimate the plane of the print bed


      #define ABL_PROBE_PT_1_X 0
      #define ABL_PROBE_PT_1_Y 0
      #define ABL_PROBE_PT_2_X 115
      #define ABL_PROBE_PT_2_Y 0
      #define ABL_PROBE_PT_3_X 115
      #define ABL_PROBE_PT_3_Y 190


  #endif // AUTO_BED_LEVELING_GRID