NWC Chart, page-146

Capping to accumulate in my view occurs when a rather large amount of shares are put up for sale, just above the trading range, forcing impatient sellers to go beneath that price.The capper, it is thought, then picks up those shares because his intent was never to sell the amount of shares up higher, merely to obtain more shares cheaper. Caveat -Sometimes this is not the case, however, and a seller simply wants out and puts perhaps their entire holding up for sale at the one time (Why someone would do this now on NWC is inexplicable).
Looking at the buy/sell sides, when someone puts up a large number of shares for sale (in this case 1 million shares) in the sell queue instead of spreading out their large sell order into different prices, and the buy side is stacked too puts the price into a range.

Just an observation