Square hole drill cannot be used on an electric drill, drill square holes need to fit a square hole drill drilling (mortise and tenon machine) to use. Mortise and tenon square hole drilled by the terrible + outer sleeve in the middle of the combination. OUR GUARANTEE We are confident that we offer some of the best products on the market. Therefore, we provide a 30-day guarantee. We will make every effort to ensure that you are completely satisfied with your purchase. Online shopping can seem daunting. We want you to know that there is absolutely zero risk of purchasing something. We won't make it difficult if you don't love it. We offer email and ticket support 24 hours a day, 7 days a week. If you require assistance, please contact us. Please contact customer service if you have any problems with your purchase.