When you select more than one sketch entity using the "Ctrl" key a relationship menu appears. However after you select one relationship the popup disappears. Hit "Ctrl" to get it to reappear.
When in a sketch and we have selected more than two sketch entities using the "Ctrl" key, we get a very convenient relationship popup menu with all of the possible relations for your selected entities.
But after you select one relation the popup disappears. Now, we may want to create more than one relation between the selected entities and we don't want to waste time reselecting them all, so how can we get that menu back up?
Once one relation is created and the menu disappears simple click "Ctrl" to get the menu to appear again.
By Jon Weston-Stanley
View the Video here