How do they hold on to what ever is pluged into them?
They have a springy insert inside them.
they have round holes, but my ic's have flat legs.
No problem!
also, if i insert a roung legged thing into it, can i later insert a flat legged thing into it, or will it be damaged?.
Flat legs or round legs, no problem, it can take 'em all!
Just a word of caution, the round pins you insert into turned pin IC sockets should be no larger than the pins on DIL headers, otherwise you will damage the spring insert.
JimB