Tummy sticks is the situation, commonly referred to as a game, in which two erect men cuddle closely and face-to-face causing their two erect penises, or sticks, to push upwards between their stomachs, or tummys. Sticks combine with tummys, hence the name "tummy sticks."
Chris: Hey Grant, wanna play tummy sticks?
Grant: Let's do that! Let's do exactly that!
<game of tummy sticks ensues>
Grant: Take me now, Chris! Take me now!