netbox/netbox/templates/search_form.html

<div class="row" style="padding-bottom: 20px">
    <div class="col-md-12 text-center">
        <form action="{% url 'search' %}" method="get" class="form-inline">
            <input type="text" name="q" value="{{ request.GET.q }}" placeholder="Search" id="id_q" class="form-control" style="width: 350px" />
            {{ search_form.obj_type }}
            <button type="submit" class="btn btn-primary">Search</button>
        </form>
    </div>
</div>