As a general rule I, 2 and 4 I.B. blocks have an oval eye for which a shackle is required, whereas similar metal blocks have a shackle permanently fixed in the eye.
Ngokomthethlo -1, 2 no -4 I.B ibloko zinentunja embhoxo apho ikhamandela lifumanekayo, apho amalaphu afanayo ebloko anekhamandela elifakwa isigxina.