#include <bits/stdc++.h>
using namespace std;
int main() {
  int t;
  cin >> t;
  while (t--) {
    int n;
    cin >> n;
    vector<pair<int, int>> cord;
    for (int i = 0; i < n; i++) {
      int x, y;
      cin >> x >> y;
      pair<int, int> temp = make_pair(x, y);
      cord.push_back(temp);
    }
    sort(cord.begin(), cord.end());
    string ans;
    int currx = 0, curry = 0;
    bool flag = 1;
    for (int i = 0; i < n; i++) {
      if (cord[i].first < currx || cord[i].second < curry) {
        flag = 0;
        break;
      } else {
        string str;
        for (int j = 0; j < (cord[i].second - curry); j++) {
          str += 'U';
        }
        for (int j = 0; j < (cord[i].first - currx); j++) {
          str += 'R';
        }
        sort(str.begin(), str.end());
        ans += str;
      }
      currx = cord[i].first;
      curry = cord[i].second;
    }
    if (flag == 1) {
      cout << "YES" << endl << ans << endl;
    } else {
      cout << "NO" << endl;
    }
  }
}
