Abstract M-theory on compact eight-manifolds with Spin(7)-holonomy is a framework for geometric engineering of 3d N=1 $$ \mathcal{N}=1 $$ gauge theories coupled to gravity. We propose a new construction of such Spin(7)-manifolds. based on a generalized connected sum. where the building blocks are a Calabi-Yau four-fold and a G 2-holonomy manifold times a circle. https://smokeysmountainfurnitureoutlets.shop/product-category/lateral-file/