The wjFlexGridFilter binding must be contained in a wjFlexGrid binding. For example:

<p>Here is a FlexGrid control with column filters:</p>
<div data-bind="wjFlexGrid: { itemsSource: data }">
    <div data-bind="wjFlexGridFilter: { filterColumns: ['country', 'amount']  }"></div>
 
    <div data-bind="wjFlexGridColumn: {
        header: 'Country',
        binding: 'country',
        width: '*' }">
    </div>
    <div data-bind="wjFlexGridColumn: {
        header: 'Date',
        binding: 'date' }">
    </div>
    <div data-bind="wjFlexGridColumn: {
        header: 'Revenue',
        binding: 'amount',
        format: 'n0' }">
    </div>
    <div data-bind="wjFlexGridColumn: {
        header: 'Active',
        binding: 'active' }">
    </div>
</div>

The wjFlexGridFilter binding supports all read-write properties and events of the FlexGridFilter class.