Explanation: Described as extremely strong, solid. Source: Lu Xun's "only _set_ of leather head" "Although this 'Beijing literary circles' has been Mr. Xu Danfu in the" learning light "on the specified will surely not be shaken, ... ...." Examples: Although this "Beijing literary and art circles" has been Mr. Xu Danfu in the "learning light" on the specified faintly ~ a, ... .... (Lu Xun's "only _set_ of leather" leader "")