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 which extends through at least a portion of the first cap member and a surface of the first cap member positioned within the bore 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 which extends through at least a portion of the first cap member and a surface of the first cap member positioned within the bore defines first threads ; and an external surface defines second threads ; and a bore which extends through at least a portion of the first cap member and a surface of the first cap member positioned within the bore 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 . <EOS>