from yahoo finance16 Apr 2010 18:54
Market Makers (MM) will "signal" moves in advance buy using small amounts of buys or sells as "signals". The "signals" are such a small amount of shares (worth no more than 5 or 10 dollars) that no trader would have paid a commission that costs more than the amount of shares bought. The "signals" are from one MM to another.
100 I need shares.
200 I need shares badly,but do not take the stock down.
300 Take the price down so I can load shares
400 Keep trading it sideways.
500 Gap the stock.
if you look just before the big buy there was a buy of 200 shares!