It is common for fastener distributors or manufacturers without heading capabilities to attempt to supply a rod with a tack welded nut instead of a headed anchor bolt. These products are not identical and it is not advisable to make any configuration changes, such as the above example, without the approval from the engineer of record. For example, when an engineer specifies a headed anchor bolt they may know that the grade of bolt detailed is not weldable. Keep in mind that any unapproved configuration changes may open your company up to liability issues.