Panels a, b and f and crossbar h with aircraft-grade aluminum?

A B F和横木H都换成航空铝？

They made the center crossbar so that it extended from end to end at the middle of the frames.

使腰间的中闩从这一头通到那一头。

The center crossbar is to extend from end to end at the middle of the frames.

腰间的中闩要从这一头通到那一头。

Other writers have learned the basics while serving in the Navy, working in steel mills, or doing time in America's finer crossbar hotels.

另外有些作海军军营里、炼钢厂里，或美国精美的铁窗宾馆里熬日子的时候学会了写作的基本技巧。

Overlay the frames with gold and make gold rings to hold the crossbars. Also overlay the crossbars with gold.

要用金子包裹，又要作上的金环套闩，闩也要用金子包裹。

They overlaid the frames with gold and made gold rings to hold the crossbars. They also overlaid the crossbars with gold.

用金子将包裹，又作上的金环套闩；闩也用金子包裹。