In ModelBuilder, tool parameters can be specified, or filled in, in three ways:
- Using the tool dialog box
- Dragging and dropping data onto the tool
- Using the Connect tool
Filling in tool parameters using the tool dialog box
In ModelBuilder, tool parameters can be filled in by opening a tool's dialog box and entering values for the input and output parameters.
Learn more about using tool dialog boxes (A quick tour of tool dialog boxes)
When a tool dialog box is opened in ModelBuilder, model variables 
or layers in the map document 
can be specified for input parameters, in addition to feature classes or other data stored on disk.
To fill in tool parameters using a tool's dialog box, do the following:
- To use the tool's dialog box, right-click the tool and click Open.
- Alternatively, double-click the tool to open its dialog box.
- For data on disk, browse
to the data stored on disk, select it, and add the data.
- If the data has already been added to the model as a data variable, or if the data exists as a layer in the ArcMap table of contents, choose the appropriate data element from the parameter drop-down list. Data variables are shown with the Model Variable icon , and layers from the ArcMap table of contents are shown with the Layer icon .
- If the data has already been added to the model as a data variable, or if the data exists as a layer in the ArcMap table of contents, choose the appropriate data element from the parameter drop-down list. Data variables are shown with the Model Variable icon
Filling in tool parameters by dragging and dropping data onto a tool
Data can be dragged and dropped from the Search or Catalog windows into a model. When data is dropped into an empty section in the model canvas, the data is added as a data variable. When data is dropped onto a tool in the model, the data is added as a data variable and connected to the tool it was dropped on. If data dropped onto a tool does not connect with the tool, the data is invalid and cannot be used with that tool.
Filling in tool parameters using the Connect tool
To fill in a tool parameter using the Connect tool , a variable to be used for a tool parameter must already exist in the model.
- Click the Connect tool , click the variable in the model to be connected to a tool, then click the tool.
- From the list of available tool parameters that pops up, select the parameter to connect the variable to.