After the bidding proceeds:

1C - (Pass) -1H - (2D)
 ? : how do you raise hearts?

If you decide to support hearts, it is important to distinguish the number of hearts that you have in support. This is possible playing Support Doubles. In this situation, you double with 3-card support and therefore a direct raise shows 4-card support. This show of length has proven to be important in competitve bidding situations. For further discussions on this see the section on support doubles in Better Bidding with Bergen, Volume 2, Competitive Bidding, Fit Bids, & More. Also the reasons for explicitly showing the length of support is well outlined in To Bid or Not to Bid, The Law of Total Tricks by Larry Cohen.

Support redoubles are a variant of this. If right hand opponent doubles then a redouble can be defined to show 3 card support while a raise promises 4 card support.

Although the Support Double and Support Redouble do not promise extra values, it should be of note that a bad hand does not necessarily have to make these support bids.