It helps to make a really tight fist for this. (neatstrength.com)
Her finger movements are limited, since her hands are likely to be clenched in tight fists most of the time. (healthychildren.org)
Anyone under a year old will most likely not be a good candidate for this project as they still like to make tight fists and that just isn't going to work... this is the reason Willow didn't participate in this project. (happeningsoftheharperhousehold.net)