The AllowMerging property has two settings that operate differently from the others that do not require you to set the AllowMerging property on specific rows and columns.
Spill Setting
The Spill setting causes text that is too long to fit in a cell to spill into empty adjacent cells. The resulting behavior is similar to the one in Microsoft Excel. If you type a long entry into a cell and the adjacent cell is empty, the entry will spill to occupy as much room as needed.
For example, the picture below shows what a grid might look like when AllowMerging is set to Spill and the user types entries of varying lengths:
Nodes Setting
The Nodes setting is similar to Spill but only applies to outline nodes. This setting is useful when data is organized into groups, and the node rows contain information in a format different from the data rows.
For example, the picture below shows what a grid might look like when the data is grouped and summarized using the Subtotal method, and then AllowMerging is set to Nodes:
This image is similar to the one in the Creating Subtotals topic. The difference is that the subtotal rows (nodes) now spill onto empty adjacent cells, improving the appearance of the grid.