Sentence:  A fiber optic splicing device may be equipped with V-grooves or <WSD>chucks</WSD> to hold the two pieces of fiber optic filament to be spliced. If it has <WSD>chucks</WSD>, they are typically either clamping <WSD>chucks</WSD> or vacuum <WSD>chucks</WSD>. 
Meaning of the word marked with <WSD> tags:  A mechanical device that holds an object firmly in place, for example holding a drill bit in a high-speed rotating drill or grinder.