Can you hold the flagstick and make a putt at the same time?
Yes. This is a question that pops up a lot. The confusion seems to have arisen because everyone thinks it was illegal a long time ago. I have seen no proof that it ever was against the rules although have some recollection of it.
You can putt and hold the pin at the same time. Don’t let anyone tell you otherwise. Make sure the ball does not strike the flagstick (Rule 17-1/5). If so, it is a loss of hole in match play of a two stroke penalty in stroke play.
Can the flagstick rest against me while I putt?
Well, yes and no. If it is deemed to be used to steady yourself it can be contrary to Rule 14-3 which states; “…the player must not use any artificial device or unusual equipment, or use any equipment in an unusual manner: a. That might assist him in making a stroke or in his play” and you may face disqualification.
In truth, the flagstick resting against you doesn’t really constitute assistance to playing a shot but it is possible it may raise some eyebrows among the rules sticklers. Avoid it.