Letters that make double-crossing
s, o, b, d, e, g, l, n, c, r, i, u are letters that make 'double-crossing'
Words within double-crossing
CRO, os, OS, DO, do, si, Ross, ng, Cross, Ro, SI, SS, cross, double, in, crossing, sin, IN, Sin, LE, Cr, In, Os, Si, sing are words within 'double-crossing'