Product Comparison liquid file linked from: https://support.boldcommerce.com/hc/en-us/articles/210227183-Product-Comparison-Install-Instructions

bold-compare-trigger.liquid

{% assign bold_metafield = bold_product.metafields.bold_spec %}
{% assign bold_meta_size = bold_metafield | size %}
{% if bold_meta_size > 0 %}
    <div class="bold_compare_{{ display }}" data-id="{{bold_product.id}}" data-handle="{{bold_product.handle}}"></div>
{%endif%}