An adjustable-height insert, comprising: a first insert part comprising: a first flange having a first upper surface and a first lower surface; a first neck extending from the first upper surface of the first flange; and a first hole extending at least through the first neck and defined at least partially by a first inner surface of the first neck, wherein the first neck comprises a first outer surface opposite the first inner surface; and a second insert part comprising: a second flange having a second upper surface and a second lower surface; a second neck extending from the second lower surface of the second flange; a second hole extending through the second neck and the second flange, wherein the second hole is partially defined by a second inner surface of the second neck; and a plurality of radially-extending projections extending from the second flange, adjacent the second upper surface of the second flange, wherein the plurality of radially-extending projections are spaced apart about a peripheral edge of the second flange, and wherein at least some of the plurality of radially-extending projections extend along less than half of a height of the second flange, wherein the second insert part is configured to be selectively operatively positioned with respect to the first insert part such that the second inner surface of the second neck engages the first outer surface of the first neck with an interference fit, wherein the adjustable-height insert is configured to have a selectively adjustable overall height such that moving the second insert part with respect to the first insert part such that the second flange is moved towards the first flange reduces the overall height of the adjustable-height insert, wherein the overall height of the adjustable-height insert is defined as the perpendicular distance between the second upper surface of the second flange and the first lower surface of the first flange, and wherein the first hole and the second hole are at least substantially concentric when the second insert part is operatively positioned with respect to the first insert part. a first insert part comprising: a first flange having a first upper surface and a first lower surface; a first neck extending from the first upper surface of the first flange; and a first hole extending at least through the first neck and defined at least partially by a first inner surface of the first neck, wherein the first neck comprises a first outer surface opposite the first inner surface; and a first flange having a first upper surface and a first lower surface; a first neck extending from the first upper surface of the first flange; and a first hole extending at least through the first neck and defined at least partially by a first inner surface of the first neck, wherein the first neck comprises a first outer surface opposite the first inner surface; and a second insert part comprising: a second flange having a second upper surface and a second lower surface; a second neck extending from the second lower surface of the second flange; a second hole extending through the second neck and the second flange, wherein the second hole is partially defined by a second inner surface of the second neck; and a plurality of radially-extending projections extending from the second flange, adjacent the second upper surface of the second flange, wherein the plurality of radially-extending projections are spaced apart about a peripheral edge of the second flange, and wherein at least some of the plurality of radially-extending projections extend along less than half of a height of the second flange, a second flange having a second upper surface and a second lower surface; a second neck extending from the second lower surface of the second flange; a second hole extending through the second neck and the second flange, wherein the second hole is partially defined by a second inner surface of the second neck; and a plurality of radially-extending projections extending from the second flange, adjacent the second upper surface of the second flange, wherein the plurality of radially-extending projections are spaced apart about a peripheral edge of the second flange, and wherein at least some of the plurality of radially-extending projections extend along less than half of a height of the second flange, wherein the second insert part is configured to be selectively operatively positioned with respect to the first insert part such that the second inner surface of the second neck engages the first outer surface of the first neck with an interference fit, wherein the adjustable-height insert is configured to have a selectively adjustable overall height such that moving the second insert part with respect to the first insert part such that the second flange is moved towards the first flange reduces the overall height of the adjustable-height insert, wherein the overall height of the adjustable-height insert is defined as the perpendicular distance between the second upper surface of the second flange and the first lower surface of the first flange, and wherein the first hole and the second hole are at least substantially concentric when the second insert part is operatively positioned with respect to the first insert part.