Insert keyframes at once

[quaker]

How do I insert keyframes on all frames at once, for example at 50 frames?

[neilmmm]

drag down on the timeline over all the layers you wish to add a key frame and press f6

is this what you mean?

[quaker]

Thanks for the help! Actually is done.
It's pretty simple, select the frames and with the right mouse button select Convert to keyframes.