fvtt-crucible-rpg/templates/item-feat-sheet.html

<form class="{{cssClass}}" autocomplete="off">
    <header class="sheet-header">
        <img class="item-sheet-img" src="{{img}}" data-edit="img" title="{{name}}"/>
        <div class="header-fields">
            <h1 class="charname"><input name="name" type="text" value="{{name}}" placeholder="Name"/></h1>
        </div>
    </header>

    {{> systems/fvtt-crucible-rpg/templates/partial-item-nav.html}}

    {{!-- Sheet Body --}}
    <section class="sheet-body">

      {{> systems/fvtt-crucible-rpg/templates/partial-item-description.html}}

      <div class="tab details" data-group="primary" data-tab="details">
        <ul>
            <li class="flexrow"><label class="generic-label">Add feat die  ?</label>
              <label class="attribute-value checkbox"><input type="checkbox" name="system.isfeatdie" {{checked data.isfeatdie}}/></label>
            </li>

            <li class="flexrow"><label class="generic-label">Add SL  ?</label>
              <label class="attribute-value checkbox"><input type="checkbox" name="system.issl" {{checked data.issl}}/></label>
            </li>

            {{#if data.issl}}
            <li class="flexrow"><label class="generic-label">SL value</label>
              <input type="text" class="" name="data.sl" value="{{system.sl}}" data-dtype="Number"/>
            </li>
            {{/if}}

          </ul>
        </div>
    </section>
</form>