A stack or assembly of fluid, mechanical, and/or electrical components permits removal of some components for maintenance, without compromising the fluid integrity of the remainder of the assembly. A fastening bolt, attached to at least one fluid component, is screwed into a stacking bolt, attached to another fluid component, the bolts being screwed together inside the bore of an adapter plate. A resilient insert sits between the head of the stacking bolt and the bore. At least a portion of the bore has a continuous taper, such that the diameter of the bore decreases in the vicinity of the insert. The taper creates a reduced diameter hole on one surface of the adapter plate, thus preventing interference between fluid ports on an adjacent fluid component. The taper also prevents loss of the insert during transportation and storage, and prevents undesired extrusion of material of the insert when the components are fastened together.