(a) Enclosures shall be by means of walls, mesh work, grille work, or slatted partitions, set flush with all floor openings at landing sides, except that landing gates of an approved type may be operated inside of hoistway, in which case the projecting saddle or sill, if more than one inch, shall be guarded as required in section 8-1.17.

(b) Wire mesh when used shall be not less than No. 10 U. S. gauge; expanded metal when used shall be not less than No. 13 U. S. gauge; the openings shall not exceed one and one-half inches.

(c) When grille work is used there shall be not more than one and one-half inches space between any two members, except where plain straight bars are used not filled in with scroll, there shall be not more than one inch space between members.

(d) Wood slats shall be not less than three-eighths inch thick, spaced not more than one inch between slats.

(e) All of the above shall be properly braced and securely fastened.