block cover

基本解释

Pure copper-base material water block provides excellent heat transfer, and anodized water block cover prevents corrosion.
纯铜基料水块提供优良的热传导，阳极氧化和水锁盖防止腐蚀。
It includes: the out oscillating flow tube, the inner oscillating flow tube, the thermal insulating block cover and the glass vacuum tube.
包括：外层振荡流热管、内层振荡流热管，保温堵盖、玻璃真空管。
ip.com
Hydraulic Disc Piston Press is all-in-one designed for hydraulic brake piston press, bleed block & cover and rotor truing fork for convenient pack and use.
本产品为携带收纳与操作之便利性，系将活塞推杆、档块及碟盘调整器等工具整合设计成一支多功能之油压碟煞维修工具。

The second suggests that a rod-like plug can block the hole by slipping across it sideways and stopping large ions from passing, rather like a drain cover stops leaves from entering the mouth of a pipe.
ECONOMIST: Synthetic biology: Expanded vocabulary The