Q:

How do I locate child element using protractor locators? 

Can you suggest locator for <input> element in the following DOM?  by.repeater only gets me till    <td>   element.  Any subsequent protractor locator is not locating <input> element underneath.  Thank you in advance! 
<table class="table table-striped table-hover">
    <thead>
    <tbody class="ng-scope" ng-repeat="devices in collection track by $index" >
        <tr class="ng-scope ng-isolate-scope"  st-select-row="devices" st-select-mode="single">
        <td>
            <chk-select class="ng-isolate-scope" emitselectedrec="selectedRows" chkmode="multiple" rowobj="clusters">
                <input type="checkbox" ng-transclude="" ng-click="pushToSelected(row)" uid="1">
           </chk-select>
        </td>
      </tr>
    </tbody>
</table>

A:

What if you would rely on the chk-select element and it's rowobj attribute:
element(by.css("chk-select[rowobj=clusters] input[type=checkbox]"));

