The Solid Wood Soldiers are a Texas-based white supremacist prison gang. Their primary tattoo consists of the initials SWS, with the two S's represented by lightning bolts. Above the initials appears the image of a bear claw, with the number 4 in the middle and sometimes the letters HCRL.
The number 33 is used by Ku Klux Klan adherents to signify the Ku Klux Klan: since the 11th letter of the alphabet is K, three Ks signify "KKK" or the Ku Klux Klan. Klan members will frequently follow this with the number 6, to indicate the historical "era" of the Klan they think the Klan currently is in.