A cap assembly for enclosing and electrically isolating an end portion of a metallic bolt assembly extending from a surface, the cap assembly comprising: a first cap member that includes: a bore (40, 40') which extends through at least a portion of the first cap member and a surface of the first cap member positioned within the bore (40, 40') defines first threads; and an external surface defines second threads; and a non-conductive second cap member includes: a sidewall which defines a receptacle with an opening which provides access for the first cap member to be positioned within an interior of the receptacle; and the sidewall of the receptacle includes an interior surface which defines third threads configured to engage the second threads of the external surface of the first cap member, wherein: the third threads extend a first distance along a length of the interior surface of the receptacle and the second threads extend a second distance along a length of the external surface of the first cap member; and the first distance is greater than the second distance wherein the second cap member is configured to, in use, enclose the end portion and abut the surface. a first cap member that includes: a bore (40, 40') which extends through at least a portion of the first cap member and a surface of the first cap member positioned within the bore (40, 40') defines first threads; and an external surface defines second threads; and a bore (40, 40') which extends through at least a portion of the first cap member and a surface of the first cap member positioned within the bore (40, 40') defines first threads; and an external surface defines second threads; and a non-conductive second cap member includes: a sidewall which defines a receptacle with an opening which provides access for the first cap member to be positioned within an interior of the receptacle; and the sidewall of the receptacle includes an interior surface which defines third threads configured to engage the second threads of the external surface of the first cap member, wherein: the third threads extend a first distance along a length of the interior surface of the receptacle and the second threads extend a second distance along a length of the external surface of the first cap member; and the first distance is greater than the second distance wherein the second cap member is configured to, in use, enclose the end portion and abut the surface. a sidewall which defines a receptacle with an opening which provides access for the first cap member to be positioned within an interior of the receptacle; and the sidewall of the receptacle includes an interior surface which defines third threads configured to engage the second threads of the external surface of the first cap member, wherein: the third threads extend a first distance along a length of the interior surface of the receptacle and the second threads extend a second distance along a length of the external surface of the first cap member; and the first distance is greater than the second distance wherein the second cap member is configured to, in use, enclose the end portion and abut the surface. the third threads extend a first distance along a length of the interior surface of the receptacle and the second threads extend a second distance along a length of the external surface of the first cap member; and the first distance is greater than the second distance wherein the second cap member is configured to, in use, enclose the end portion and abut the surface.